How far from Earth is the Breen Homeworld? Their entire evil plot read like they were just receiving the TV signals from Earth and catching up on the show 24. Talk about a rube goldbergian plot! They went through about 15 different evil sub-plans (each of which would have been more effective than their actual endgame plan) in order to try and steal a crashed ship from a planet that no one knew was there?
Along the way, they frame (but don't bother to eliminate) Data, almost kill the Gorn monarch and the Fed President, kill and replace several other people, leave clues to string along the Enterprise, etc. Wouldn't any of those plans by themselves have been better? At the very least, follow through and finish it, and you're better off.
And in the process, burned an android avatar spy program that they spent a ton on, and years of effort.
All in the effort to get better propulsion tech. Since they were able to infiltrate anywhere they liked and replace people, wouldn't it have been easier to just have one of them replace a Starfleet officer and just steal the Quantum Slipstream blueprints? Nice and easy, doesn't even reveal your android program. Or hell, could have just borrowed some Romulan tech and cloaked the damned crashed ship, towed it home for later. Either of those plans gets the same result (or better, successful) with far less effort and risk.
To make it worse, spent half the book breaking the fourth wall by having the characters tell us how stupid this plan was! Was at least expecting the reveal to be bigger, and those characters to be wrong, but they pretty much nailed it. Disappointing, in that my mind built this up like the Breen had a clue what they were doing. Not so much...
Didn't hate the book, just felt like a letdown after all the buildup, and not nearly as much fun as the first one.