Notes from MSB in 2021:
Many believe Samuel wrote this book, somewhere around 1000 BC.  David's name is mentioned in the book, but not Solomon.  However, there are no features and no testimony that verify this.  The author is just a guess.  "What Venus is to statuary and the Mona Lisa is to paintings, Ruth is to literature."
MSB says the story likely occurred during the judgeship of Jair, 11-26-1105 BC.  This is a best guess though.  The famine in the story is not mentioned in the book of Judges so it is no help in the dates.  I suppose we have no weather or climate records from other sources that might narrow it down.  Ruth and Boaz are mentioned in the lineage of Christ, making them real people who lived and loved and had children, not just invented characters in a beautiful story.
The book of Ruth is accepted as canonical by the Jews, and is part of the Megilloth, or "five scrolls".  Each of the five books is read by Rabbi's at a certain time of year.  Ruth is read at Pentecost because of the harvest scene in the book.  

Chapter 1
First verse tells us this story occurs during the time the judges are still ruling Israel.  Elimelech is introduced, and we see that he is already married, has two sons, and lives in Bethlehem..

2022 - There are a lot of references to Bethlehem in Judges, and now yet another in Ruth.  Bethlehem is not some obscure place that only shows up with the birth of Jesus.  In fact, it is mentioned 39 times in the Old Testament.  Only in the 39th instance is there a prophecy about it being the birthplace of the Messiah.  But the point is that Bethlehem, though small, figures prominently in OT history.  Around Christmas, this might be a good post, giving the broader history of Bethlehem.

During a famine, Elimelech takes his wife and two sons to live in Moab.  Elimelech dies there.  The sons take Moabite wives, and then they die in Moab.  They've all been there about 10 years.
Naomi decides to return to Israel because she has heard that there is food in Israel - the famine there has past.  Moab was apparently still in famine.  

2022 - Here are the verses:
6 Then she arose with her daughters-in-law to return from the country of Moab, for she had heard in the fields of Moab that the LORD had visited his people and given them food. 7 So she set out from the place where she was with her two daughters-in-law, and they went on the way to return to the land of Judah. [Rth 1:6-7 ESV]
Naomi decides to go "home" because God is there, and she's heard He is taking care of His people there.  She believes that even though her connections with that country have grown dim with time that being in the vicinity of people whom God is blessing will have benefits for her also.  In those days, travel was a very dangerous thing for anyone.  It's not like they had freeways, or highway patrols, or even local sheriffs to keep the roads safe.  For three women traveling alone, this was a very very perilous journey.  Naomi judged the benefits of proximity to the people of God worth the risks involved in getting to them.
There is a FB post here...Maybe it is a big step to get ourselves back in church after being gone for many  years. Maybe we worry about the fallout from friends and family if we try to break from a life with no real purpose and go back to a place where we were once fulfilled and at home.  Back to a place where all seemed right.  The perils of the road are real, but the possibility of being welcomed back into the presence of God's people, and the sharing of God's blessings on them, is worth those risks. In Naomi's case, the risks turned out not to be as serious as she imagined.  It is always worth risking the dangers of the road in order to get home.  So make a plan, get packed, and take that first step toward home.

Naomi has been well treated by her daughters-in-law, and tells them to go back home, where they have a good chance of marrying again, and having a good life.  Her prayer for them, her wishes for them, are very touching.  The relationships are apparently very close, because both women declare that they would rather go back to Israel with Naomi.  Naomi apologizes to them that their troubles are the result of God's hand being against her (Naomi).  

2022 - This is the verse:
13 would you therefore wait till they were grown? Would you therefore refrain from marrying? No, my daughters, for it is exceedingly bitter to me for your sake that the hand of the LORD has gone out against me." [Rth 1:13 ESV]
Naomi's bitterness is not because of her own poor lot in life.  She isn't feeling bad for herself at all, but is following on with whatever God has in store for her.  Her hopes are for her daughters-in-law, who have become collateral damage from Naomi's hardships.  Even at such a time, facing the hardships of a long journey, her care was for those who'd been kind to her and to her sons.  This is the key to maintaining our faith when things are rough.  We ought not turn our thoughts inward and dwell on our own hardships, but look outward, and look for ways to help others who are suffering also, often from exactly the same circumstances.  I am convinced that if we focus on making things better for others we can better cope with our own circumstances.
Possible follow up post...

She tells the girls they have little hope of ever marrying, ever having children, every being truly happy really, if they go with her.  Even so, Ruth chooses to accompany Naomi back to Israel.  Orpah goes back to her parents.
This verse:
21 I went away full, and the LORD has brought me back empty. Why call me Naomi, when the LORD has testified against me and the Almighty has brought calamity upon me?" [Rth 1:21 ESV]  We can see here that even the presumably random effect without cause events that led to Elimelech and the two sons dieing young in Moab are attributed to the direct action of God in Naomi's life.  She saw these events as being about her.  We saw this belief also in her apology to her daughters-in-law.  She believes she is marked by God for trouble, and we can infer that she believed there was some sin in her life that had caused it all.

Chapter 2
We learn about a relative of Elimelech who is wealthy, has a good reputation, and lives and farms in Bethlehem.  Somehow, Ruth decides to place herself within his circle by gleaning in his field.  Think of this.  She and Naomi are very poor, with no man to support them.  They don't work in a restaurant as waitresses, but instead are allowed by Mosaic Law to go behind the harvesters and collect what has been missed in the picking.  A pretty chancy thing to depend on for your basic needs.  They might get enough to eat most days, but are unlikely to be able to buy new clothes, shoes, or pay the rent, etc.  So instead of just trusting to chance, Ruth realizes that there is a possible connection - an upgrade - with this wealthy kinsman of Elimelech, and she puts herself in position to interact with him.  Ruth goes to glean after the reapers.  Sure enough, on apparently the first day, Boaz comes to the field and spots her.  Boaz asks about her.  That is, he notices her because she "stands out" among the poor who are gathering after the gleaners.  Not only that, but when he asks the foreman, the foreman has also noticed her and paid attention to her all day because he points out that she's taken only one short rest the whole time.  This woman mush have been quite attractive.  
Boaz tells her to stay always in his field to glean.  He takes interest in her, gives her special treatment, and instructs his workers to favor her also.  The young men were to leave her alone.  Her looks have brought her the favor of Boaz, but they also bring danger from the unscrupulous.  She isn't really "hired", because she's only picking up the leftovers, but she is given a safe location to eek out a living for herself and Naomi.  This was a big deal for them.  Boaz is a kind man.  Apparently there are also other young women, possibly with similarly trying backgrounds, and he seems to be purposely throwing some support their way.  Into this benevolent circle he invites Ruth.  Boaz tells her that his kindness is a return for the kindness and loyalty she showed to Naomi.  Their story is well known in the area, and Boaz is well aware of it, and believes Naomi is due some good fortune.
At lunch, Boaz invites Ruth to eat with him.  He shares bread, wine, and roasted grain with her.  Apparently this goes well, because afterwards, he tells his workers to let her gather in areas not yet harvested, rather than just picking up the leavings.  And he tells them to leave some harvested grain, all bundled for processing, so that she can have that also.  This is like a waitress getting a hundred dollar tip.  Even more, Ruth will continue in this capacity through barley and wheat harvests, so she and Naomi will eat well for a month or two, and possibly have enough excess to carry them through the year.
Note - I was wrong when I said Ruth purposely went into Boaz's field.  We see in vss 17-23 that Ruth did not know Boaz at all, and that her presence in his field when he arrived and noticed her was just chance - the kind of chance that God arranges.  We get some more insight into the social station of these women from this verse:
22 And Naomi said to Ruth, her daughter-in-law, "It is good, my daughter, that you go out with his young women, lest in another field you be assaulted." [Rth 2:22 ESV]  It seems likely that Ruth might have been raped in the fields and then had no real legal redress against those who did it because of her low social status.  This was not how it was supposed to be, but we have seen from the book of Judges that Israel was not a very good place in some places.  Boaz has not just offered Ruth food but also security.  She had a good day!

Chapter 3
In the first five verses, Naomi suggest a plan to get Ruth even closer to Boaz.  We don't know if she devised this herself, or God revealed the plan to her.  MSB indicates that the sleeping at Boaz's feet was some sort of "social convention" of the time and place.  It seems to have been designed to inform Boaz that Ruth was available for marriage.  Being a good man, and much older than Ruth, it is unlikely that Boaz would ever have made overtures to Ruth had she not made him aware of her willingness.  So Ruth sleeps at Boaz's feet.  He is flattered that she sleeps near him and not near the young men, and promises to redeem her if a nearer kinsman does not.  Ruth could have laid down at the feet of any strong young rich man with potential.  Or she could have picked the best looking.  But with Naomi's advice, she lays at Boaz's feet, and he accepts her - was likely wishing for some way to take Ruth in - and promises to both redeem her, redeem Elimelech's land very possibly so that Naomi would have a source of income, and to marry Ruth.  Another very good day for Ruth.

Chapter 4
Boaz contacts the nearer kinsman, who refuses to buy Elimelech's property, lest he mar his own inheritance.  In the custom of the time, to make his proposal to the nearer kinsman, Boaz also invites ten elders of the city as witnesses.  With the formalites in place, Boaz confronts the nearer kinsman.  In this setting, that kinsman must answer, once and for all, as to his intentions.  So the way it worked was that if the kinsman redeemed Elimelech's land by buying it, then he also had to marry Ruth, the widow of Elimelech's son.  And their child would inherit the land so that it stayed in Elimelech's family, but further, this child would also receive inheritance of land the kinsman already owned.  A share of it, not all of it.  The note in MSB adds that Naomi was trying to sell this land so that she could use the money to support herself.  In the year of Jubilee, it would be returned to her, and presumable she could sell it again, and continue to survive in this manner.  It also says that marrying Ruth was not strictly required by the levirate laws.  MSB says perhaps Boaz was looking at the law's intention, rather than just it's letter, and so made the proposal to the kinsman in this way.  Further, MSB says it is likely that the kinsman was either Boaz's brother or cousin.  It may also have been that local custom in Jerusalem was to marry the widowed daughter if you redeemed the land.  We really cannot be sure why the marriage is presented as a "requirement" instead of as an option, as we would expect.  
But Boaz redeems the land, and takes Ruth for his wife.  She has a son, who is named Obed, who is the father of Jesse, who is the father of David.