There are alternatives to Adsense??! I bet the book says to try affiliate links from places like CJ and Linkshare and to try Adbrite, Bidvertiser, etc.
Wrong, although those are included...along with an additional 25 or so. As well as bonuses... As well as 100% instant commission...
And I assume they didn't just copy/paste this one: http://www.johnchow.com/other-advertising-networks-besides-google-adsense/ ; I think it contains more than enough.
I agree that it is more than enough. That is why an explanation of the 25 best ones is given and why it will work for you.
You don't need to spend money to find out about other advertising methods. Especially since it is cheaper to just go through the trial and error method of giving them a shot and asking friends for recommendations. Who knows, you might even earn some cash while you experiment around with them.