So B. It is the type of book where you quickly have to suspend your disbelief, but it makes it worthwhile in doing so. Young Heidi lives with her severely mentally retarded mother and a guardian who is scared to leave the house. Heidi plays a big role in the household as the only one who can go out and be trusted to make purchases (or to win money from the nearby slot machine). But when some old photos give her a hint into her mother's past, she takes a cross-country journey to see if she can find out where she belongs.
The characters are what makes this book work. Heidi is a strong narrator, and her quest is compelling enough to carry the story, which has a fairy-tale like feel to it.