I reviewed the book for the New York Post and later defended it against Matt Welch's knowledge-free criticism. I also got in touch with Frum and when he started FrumForum I went on to write a number of articles there; I hope to write more for that site in the future.
Comeback didn't influence me so much by changing my mind with its policy prescriptions. I was impressed by many of Frum's proposals and disliked a few (e.g., a "war on obesity"), but had a lot of common ground politically with Frum before I read the book. No, what was influential was the growing recognition (sparked by the book, increasing thereafter) that Frum's emphasis on rethinking policy -- or indeed thinking about it at all -- made him more and more an exception on the right; that instead, ideological orthodoxy, infotainment values and paranoid hysteria were pervasive and that these tendencies were manifest in both conservative and libertarian circles.
Frum's forced resignation has convinced me the sclerosis of the right is even worse than I thought. It's a condition that will be hard to cure, if that can be done at all.
UPDATE: Frum's post: "So What Happened?"
UPDATE 3/27: Tunku Varadarajan reiterates the amazing theory that the reason for Frum's termination was "goldbricking," i.e. he wasn't doing much work there so why pay him? I highly doubt that, given (a) the timing, coming right on the heels of Frum's controversial "Waterloo" piece and the WSJ's denunciation of him, and (b) one would think AEI would've asked him to do more work, if that was the issue, rather than firing him, especially in that (c) he was one of the best-known people they had. But if the "goldbricking" theory is true, then AEI is guilty not of ideological orthodoxy but of something even worse: stupidity. Did they not notice the timing and how Frum's termination would be perceived? As John Aloysius Farrell puts it:
If AEI was not punishing Frum for his apostasy, then its timing was at the very least awful, and the episode handled with a clumsiness that Larry, Moe, and Curly would admire.
UPDATE 3/28: Also see John R. Guardiano on "David Frum vs. the Right's Company Men."