Just wait till you get the fabled "1 cent residuals check" ;)
As someone who's looking to get published (scary thought, right? ;) I see these sorts of books (or really any opportunity to be published) as a great opportunity to:
- Help out other game developers! What better way to get people to like you than to solve problems for them? :) I've gotten a lot of value out of the various gems and collection books out there, so it feels good to give back, too.
- Get your name out there. Writing an insightful article is a great way to have people know who you are - "Oh, you wrote about that neat XYZ technique, didn't you?" Which leads us to...
- Builds your career. If you're known and respected in the industry, that means you're more hireable and you're more valuable to employers, too. So you win cuz you might be able to command a better salary, and employers win because they know you're a fantastic guy who's worth hiring. :)