What Linda said! Not only is Darren the ultimate ProBlogger, he's also a very nice guy to boot (I did some blogging for him a long while back).
As for the book, I don't have it yet, but there's also a forum which has some good info on it. So, if you're on a tight budget, check out the forum and read some of those tips.
I also have his other book, aptly titled Problogger (Secrets for Blogging Your Way to a Six-Figure Income) and I must say it's a nice little book for anyone who's just starting out in blogging or who isn't already making as much money from his blog as he'd like to. Frankly, I'd recommend the book if for no other reason than the selling a blog section.
~ Teli