The Limits of Google

There is a book by Mildred D. Taylor, titled Roll of Thunder, Hear My Cry. I've turned that phrase into my declaration of exasperation. I did a search on Google to see if anyone else uses that phrase that way. Apparantly not, but Google apparantly thinks that Taylor misspelled the titled of her own book.

Why does Google suggest Role of Thunder, Hear My Cry as a better search? Are too many people mistyping the title like that?