I'm fascinated by this case and have read several books about it. I found this one to be the "best" in the sense that I think it's the most comprehensive (and, in fact, exhaustive; it takes a long time to plow through this one.)

One of the more interesting things about this case is the fact that everyone involved blames someone else, including the authors of the various books that have been written; in some cases they even criticize each others' books. I'll just say that there's enough shoddy investigation, shady stories, outright lying, contradictory evidence, etc., to go around. Be that as it may, I think that this is probably the best book to start with for anyone who is interested in this case, because it seems to contain the most detail, and is relatively objective.

FYI - this was made into a miniseries a few years back, which I found mediocre at best.