The episode certainly wasn't based on the book. The makers of the show were too busy making the show to pay much attention to the books, and if they had based it on a book, they surely would have credited the original author, otherwise it would've been plagiarism.
It's very, very common for different writers to come up with similar ideas, especially when working on the same series.
That's a fair point. And I suppose if Cardassians are involved, including Garak at some point is almost unavoidable.
While I'm still finishing Station Rage
, I intend to buy a few books this weekend...Plagues of Night, Forgotten History
, and perhaps a Vanguard novel.