It's the story of two guys (a manic depressive former minor league ball player (and former small town baseball hero) and a teacher) who are found guilty of murder when a more obvious suspect is available and more likely to have committed the crime.
The book's irritating because from page one you're thinking "Yeah, but why aren't they looking at this guy as a suspect?" and wondering whether this is what justice looks like if you're poor or behave weirdly in small town America (I'm afraid to say that having read the book, the answer is that you had better watch probably).
In addition to the irritation I felt while reading this book, part of me wonders if this book could have been better presented if it was written more like a typical whodunit and we weren't presented with who did it on page one. This might have been problematic, however, because the prosecution had so many holes in it that the reader might have found it hard to buy into the story.
My other grumble is that I wanted Grisham to give is a call to arms at the end of the book and tell us what to do, but he didn't, so you better not expect one when you finish the book.