If I'm interested in reverse engineering, but at a higher abstraction than this book - let's say there is a game client communicating with server and I want to understand what the format of the packet is (ie. application level rather than all the way down) - does the question make any sense? And where could I find material for it?
Wireshark, Deep Packet Inspection and similar might be terms you can look after to find out more. RFCs are what you need to understand the protocols (if they are public standards)
I thought linking to the source rather than to just the pdf would be more useful for you, as a) some might like to actually contribute and b) many would like to know what else the author made and lastly c) a minority of people isn't allowed to open pdf's from the internet, so they could build it locally (or just starr on github).
Apart from working out which .tex file corresponds to which piece of text, the files are tricky to read because they contain both english and russian strings delimited by some kind of macro.
Why do you write [an entire kernel, an operating system, an RDBMS, a web application framework, ...] and offer it for free? Sometimes, the journey of creation and the sharing are more important than any remuneration you might otherwise get.
I hope he publishes a print version of the finished book, like Miran Lipovača did with Learn You a Haskell for Great Good! If someone releases a free book that has immense value to me, I'm more than willing to support them by buying a wonderful print version. There's something wonderful about having the ergonomics of a print book, combined with the ability to copy and paste and follow links from a PDF...
Well, I've got nothing close to a 600 page book, but I offer a number of smaller documents at the website for my side business, plus some software and other design tools. If I have any ulterior motive, it's that those materials give me some technical credibility and maybe generate a bit of goodwill.
Has it helped? Over the years, it's gotten me a little bit of "buzz" on web forums, and has attracted a couple of people who wanted me to do custom work for them. Also, in a manner akin to OSS, a couple people have been kind enough to report mistakes in my documents.