I have to say I enjoyed the book, even though it was not quite what I was expecting. The cover led me to expect a plot similar to the Armageddon/Deep Impact films but, apart from having a comet heading for earth, the plot has little in common with either. There are some nasty politics involved which, given an end-of-the-world scenario, I suspect, might be quite close to the mark and the author deals with a few uncomfortable truths that would almost certainly arise in such a case. The plot mixes in liberal dose of time travel and alternate realities and I got lost in a couple of places but, apart from that, the story works quite well. It has aliens who see the future as a matter of course and they are actually quite believable (déjà vu is a way of life - I love it!) The story is mostly told through two main characters, one alien and one human and you get to see both sides of the story - just because someone is trying to wipe out your planet, it doesn't necessarily make them a bad person - that kind of thing. There are a few colourful characters that we don't see enough of and, hopefully, they will return in book two. There are one or two nasty twists and it's worth a read just for the ending. The typos are minimal and the writing style is good, the book keeps you interested and it certainly leaves you wanting more. Overall, I think it's a good book, but it didn't quite have me on the edge of my seat as it could so easily have done. With a little more suspense, it could have been a great book and so I can only give it four stars. But, if you want a good read with some interesting and original ideas, then I would say it's definitely worth the money.