> I don't expect to make a huge amount of money on it, relative to the business in general, but the idea sounded attractive enough to try it as an experiment
I find this a strange thing to say.
A book is a way in which to earn additional income from content you've already produced.
Why not have the content you produce pay over and over?
Once on the blog.
The second time on the blog as a best-of-the-blog.
The third time in a book.
The fourth time as presentations at conferences.
One piece of content, earning revenue many times over. It seems to me that the book isn't supposed to earn a huge amount of money, you already spent the time creating the content and relative to the time to compile and edit the book should earn a tidy income.
And, as you are patio11 and have a great standing, the book can only further enhance your reputation and achieve higher sales, and increase your value to conferences later.
Whether or not you yet appreciate it, you are one of the few programmers who has the status equivalent to a celebrity chef, and you should seek to earn additional revenue through recycling the same content through different channels. You should, because you're one of the very few who could. For you, not writing a book is money left on the table.