I definitely went into the book expecting for there to be some animosity between Garak and Picard. But to be honest? I loved
that they got along, even going as far as to consider one another friends by the end of it. I hope its something future novels revisit. They have a lot in common, despite being on opposite spectrums of the 'good' scale.
I think by having them be friends, it shows not only how far Garak has come as a character, but also how Picard continues to be open minded. He judges people based on how he interacts with them, not on reputation alone. I came out of that book with the sense that Garak and Picard are probably two of the more reliable people in the quadrant.
Which is why Bashir continues to bother me in the novelverse. I'm not sure how much of it is intentional, and how much of it is just how he's been written lately...but it seems like he's very quick to take the moral high-ground with characters like Garak, while brushing off his own failings. His whole letter came off as sort of ironic, considering he's the one that's been off spying and killing people these days.