As a budding online player, and working in the computer industry, I had heard some buzz surrounding this book. I was anxious to see it and managed snag an early review copy.
On the whole it is excellent.
Harlan and (especially) Derossi are fairly well-known insiders in the computer industry and are working on a next-generation poker site (I think it's shown in the book as a "Modern" table, and if that's what they're doing, it's very cool). This book is different from the other online books I've read in that it focuses exclusively on the differences between what they call "brick-and-mortar" poker rooms and those online.
Refreshingly, basic poker knowledge is assumed, you won't find even a sentence in here about what-hand-beats what. Although they make continual reference to "Poker for Dummies," to learn the basics, I think you're better off with Sklansky's "Theory of Poker," Jones's "Winning Low-Limit Hold 'Em," or Miller's "Small Stakes Hold 'Em."
Their section on judging a poker site for quality is great. The bit about online pitfalls and their piece about how to read Internet "tells" are both good. The single table tournament section is the best I've ever read on that topic specifically.
There is some mention in the book of Omaha, even less on Stud, but the book (like online players, I guess) clearly has a Hold 'Em bias.
What's a little strange is, aside from the chapter on single table tournaments, you will find very little general poker strategy. So if I have any bone to pick with this book it's that it's misnamed. It shouldn't be called "Winning at Internet Poker for Dummies," instead it should be called something like, "Nuances of Internet Poker for Everyone."
Don't buy this expecting to learn how to play poker (you won't). Do buy this if you're interested in gaining an extra edge in the online world that you might otherwise miss. (Which is to say, if you're playing online, you should read this.)
