It's been quite a while since I last read one of McDevitt's books. I enjoyed Engines of God, and A Talent for War is currently his best (and also one of the best general sci-fi novels I've read in quite a while). Odyssey, however.....stay away. Like everything he's done after Engines of God, it's steeply downhill all the way. I've previously noted that e.g. Chindi wasn't great, and you're probably wondering why I went back. For one, I picked up the paperback cheaply, and for another, you begin to ask yourself, "Really, how bad can it be ? It's a book.".
It's bad. The original series of Star Trek featured prop conduits on the walls marked "GNDN" - "Goes Nowhere, Does Nothing". That'd be a great tag-line for this novel. It's more of the "Hutch/Academy" series from the earlier books ("Mac" MacAllister also puts in an appearance), but the plot and story is plodding and dull. A central theme is that space-travel is a lot of sitting in ships looking out into interdimensional misty nothingness - in short, it's boring, and my God, does McDevitt really hammer this point home, beating it into your eyes with every additional page of deeply uninteresting internal monologuing by his characters.
To wit, some apparently alien spacecraft have started showing up and been noticed by human starship pilots. Some mischief is created. Broadly in line with McDevitt's other books in the series, you ultimately find out absolutely nothing else about them of any interest, except that They Are Alien And Have Their Own Agenda. They might not even be alien; you never find out anything else about them. There is some ham-handed and tiresome ecological moralising and a feeble attempt at heroic redemption, plus an interlude about a court-case on earth which, as far as I could tell, had literally nothing whatsoever to do with the rest of the plot. As with some of his other novels, A Big Rescue is required, where you basically get several pages of excruciatingly dull tallying of numbers and a terrible attempt to build tension by, predictably, people showing up late.
I could go on, but haven't the stomach for it. You should all be grateful; I've read this so you don't have to. So please, please don't. Learn from my error.