I actually bought a book at Borders today, something I never do anymore. Computer books in particular are rare purchases for me because there are few that I need or want to learn from.
Ajax technologies have been around for a long time, it's just that they're finally be used together in really interesting ways. There's quite a bandwagon behind this stuff, much of it hype. Yes, browser-based apps are all the rage, and have been around for a long time, but there are now design patterns you can clearly identify and other people have made mistakes for you.
Do I have use for any of this? Well, I can think of a couple of instances where it may be useful to me. I guess the reason that I'm drawn to it is just that it's something new.