Discuss the theme of "the outsider" as it is manifested in this book

This should help you immensely. The theme of being an "outsider" is a strange way to put it, but you have to remember that Ruth left her family (she was disowned), made a biracial marriage (simply unacceptable in those days), and from then on existed within the heritage and culture of her husband(s).

Community

"The book contrasts Ruth's own experience with those found in the two communities to which she has belonged. On the one hand, her cold Orthodox Jewish family disowned her, turned all the mirrors in the house face-down, and declared her "dead". They refused to give her aid when her husband passed away, leaving her with eight children to raise alone. They felt that they were no longer responsible for her fate, since she "died" in the eyes of their community when she married a black man.

The black community, on the other hand, wholeheartedly embraced Ruth. Ruth describes how, when she returned from burying Dennis's body in North Carolina, she discovered the mailbox stuffed with checks and money orders and cash from many of the people who had known them. Aunt Candis and Jacqueline also arrived to help. Ruth's household was its own microcosm, a private space where her children could grow up surrounded by the members of their own unique community."