Thanks for all the ideas for which book I should write first and keep them coming! Here's one from somebody with a close-in perspective"
Don't think of the book as hitting much more of a target than one of your articles. Many nonfiction thought/policy books (of the popular rather than academic kind, anyway) these days are essentially expansions of snazzy articles -- readily-identifiable topic, great angle, a couple of terrifically catchy phrases. "The Tipping Point." "South Park Republicans." "The Long Tail." Crunchy Cons. Bobos. One thing -- of course, one thing that has enough validity so readers actually say, "Hey, yeah, I notice that too!"-- that you can get people talking about for five minutes.
It's sad that this is what most bookwriting has become. But it isn't dumb -- it's one of the few ways a book (and a book author) can poke through the media fog for a few minutes. The key realistic thing to understand is that your goal is to get people talking about the book -- which means that you want reviews, features and interviews, and to get those you have to have that one resonant thing that'll give the writers and interviewers an easy 10 second pitch. Ah, I get it -- and then they've snagged their readership. Most of these books have more of a life as a media event than they do as traditional books.
There's a certain kind of book that creates a terrific stir in the press but that doesn't actually sell very well... But that's OK for the author -- he got his advance, he's now a book author, and he's got the cred you get from 1) getting a book published and 2) getting your topic and your angle taken seriously and chatted about. That can turn into lectures, panel appearances, etc -- which often means more money than the book, as well as an elevated stature. You're no longer a wannabe (so far as the game goes), you've arrived. And that has its benefits.
The superkey thing to avoid is thinking of a book as a place where you put it all -- all your observations and thoughts. No one wants that, at least not in a commercial sense. It'd be a lovely monument to your genius, but the publisher (and the public) could care less.
Important to remember that there are multiple levels of sales going on. You have to sell your idea to your agent. The agent has to sell it to an editor. That editor has to sell it to her boss. Both of them have to sell it to their sales force and their publicity staff. The sales and p-r people have to sell it to the bookstores and the press. Eventually everyone hopes to reach the public. Two points: publishing a book is a long process. And, because there are so many levels of sales involved (and because there's so much media fog out there), you pretty much *have* to polish your subject and your angle on it to a real sharp gleam. You don't want your book to be a nonstarter, just because you feel you have more to say.