I've wanted to read this book for years, but I never could. I recently got a copy of the new reissue (although the cover is different to the one Jason mentioned, and it seems like all of Powers' books have been given this same treatment recently, at least in the UK), and I'm just over halfway through.
It's obvious that the movie isn't really going to be based on the book, aside from including the fountain of youth and Blackbeard, with integral characters such as Davies, Hurwood, Friend, etc., apparently left out of the movie. I'd have liked to see a straight adaptation of the book, though, if only to see how PoTC fans reacted to the
Dragonball Z style air-based face-off between Hurwood and Friend.
In all seriousness, though, I honestly don't think a straight adaptation of the book would have worked very well for PoTC, which now has a perfectly good life of its own without having to guiltily pay its respects to On Stranger Tides or Monkey Island.