I got this book because it was recommended in one of the comments on Scalzi's blog and sounded interesting. It was, more or less, but it wasn't really a compelling read. I had to force myself to finish it, and that's rarely a good thing.
It's an archeological story, like I understand most of McDevitt's are, and it's about the Great Filter — humanity has discovered two worlds that were home to intelligent life, and both of them have had massive extinction-level events. There are also the mysterious Monuments, left behind by yet another race that humanity has yet to find any other trace of. Unlike real-world archeology, attempting to discover the reason behind these events quickly becomes a race against time, with the future of humanity's civilization at stake.
The alien civilizations were well realized, and the particular outside-context problem in this book was excellently described. Unfortunately, the characterization is weak, and at times nonexistent, and as I mentioned above, the plotting belongs strictly in the realm of Hollywood archeology. Read it if you don't mind getting more of a setting than a story.
Recommendation: Borrow from library or buy used