Fiction by Jeanette Walls.
I was not sure whether to classify this book as fiction or nonfiction. (And I didn't get it from the library, so I don't know how they shelved it.) According to the author, it's a "true-life novel," which means it's both, I suppose.
Anyways, this is the true story of the author's grandmother, retold in first person as if the woman were actually speaking to the reader. It's a good book, and it acts as a sort of prequel to the author's first book (see below), which is a memoir and therefore squarely NONfiction.
I've mentioned it before, but The Glass Castle is a fabulous book. Reading that book had painted quite a picture of the author's mother, and now Half Broke Horses explains a little bit more about her character.