I'm a big fan of Jack McDevitt, but this book is one of the rare exceptions in his work. It's fun enough, but if you don't read it, you're not missing anything. I'd suggest that there's nothing new to say in time travel stories, but that's clearly not true. Every now and then, something new comes along (The Time Traveler's Wife, Pastwatch: The Redemption of Christopher Columbus). Okay, not hugely new, but interesting.
I'm sorry to say that Mr. McDevitt doesn't bring anything new to the party here. Mildly interesting characters, well-researched settings, but it's very much a book you can put down to sleep, eat, go out, ... The writing is technically good, as always, and it's light, but the plot is pretty much missing. Acceptable from a minor writer, but a disappointment from McDevitt.