I find the approach taken to a book does more to learn the subject than volumes of content.

For example, years ago I was trying to learn C, and had one or two of the various “teach yourself…” books on the subject. While reading through them, I came across (and purchased) the K&R book on C. I gained more by reading that first chapter than I had from all my efforts with the other books. I tossed them aside and continued on with K&R. I’ve found that books written in a similar format worked much better for me (The AWK Programming Language, The Kornshell; Command and Programming Language).

My take away from that had been the format was important, and that these books were written by the people who wrote the software.