"Jubliee" is a maturational novel. You may have heard the literary term for this, bildungsroman.
The plot, briefly: Vyry is the mother of a slave who has died. She is sent to work in the "big house" under the cruel "Big Missy." Growing up, Vyry must witnesses horrific things in addition to being mistreated. She sees a man get branded and knows many others who die.
Vyry falls in love with a freed black man, Randall Ware. Ware promises to buy Vyry's freedom, but before he is able to do so, he is forced to flee to Georgia. Vyry tries to follow him, but she is caught.
Finally, Lincoln issues the Emancipation Proclamation, but things don't become easy for Vyry or many other newly liberated slaves. The KKK makes life miserable and keeps Vyry on the run.
Evenutally, Vyry remarries a man named Innis Brown. But then she discovers Randall is not dead after all and wants her back. Vyry chooses her new life over her old.
Possible thesis: Through a series of difficult situatuion and choices, the character Vyry in Margaret Walker's "Jubliee" comes to terms with her life.