You're right that it doesn't go into detail but it's short and provides high-level overview of the most important features. It's much easier to learn the basic of something from a book and then find the details in the manual than working with the manual only.
But if someone expects to gain deep, expert level knowledge of how OpenSSH works then he'll be disappointed. What expert-level books can you recomment?
Unfortunately, I can't recommend anything, but I'm not a wide reader on the topic so my knowledge is limited.
Perhaps I was a bit hard on that book, my expectations were that it would be a deep, expert type of book. If that's not what you are looking for, it is perfectly fine. Actually, now that I think about it, the epub version is good to keep on your mobile phone as a handy, easily-accessible reference for use in the coffee shop, so I guess it does get a credit from me.
But if someone expects to gain deep, expert level knowledge of how OpenSSH works then he'll be disappointed. What expert-level books can you recomment?