I hope I don't discourage anyone, but you ought to have your eyes open regarding what you're getting yourself into.
I'm a co-author of a real dead-tree-type technical book . I did it with two other friends. I wrote about 40% of its 600 pages. The time investment necessary to accomplish this is tremendous. For about 6 months I invested every hour -- evenings and weekends -- that I wasn't actually at work (except I reserved Thursday night with my wife, we'd watch Friends
Now, I certainly got a great feeling of accomplishment out of this, and it's obviously good for putting on your resume. It will *not* get you rich.
But if you're looking to produce a substantial professional-quality book, be prepared for that kind of commitment.
 Inside ISAPI
, which is a mostly-obsolete technology for building web sites. Actually, it was mostly obsolete almost from the time the book was published. See it described here