I've really liked almost all of this author's other books, but I just couldn't get into this one, probably because I don't care for time travel stories. So if time travel's your cup of tea, you might enjoy it.
I had more trouble getting into this than most of Willis's books, but enjoyed it as it went on. It is only part one of the [presumably] two-part novel, and I would have liked to know that the second book is to be released in October 2010 before I purchased it. Cliffhangers are more fun if one can pick up the next book quickly.