50/50.
There are very murky and heavy books. There are good books, there are good authors who
explain things without snot.
But books quickly become outdated. If you buy a paper book, then in 5 years it is 30%-40% waste paper.
Books on "hardware" generally become outdated in 2-3 years.
I have a paper book about FreeBSD 5.0.
I read little useful information there. This book on version 5.0 is very different from 14.2.
The best thing is the notes.
The best thing is your notes, which you wrote yourself. With a pencil, ink or ballpoint pen.
I keep such a notebook. Then you don't need manuals, wikis, etc.
Even if there is no access to online manuals, your paper friend will always come to the rescue.
This forum is a good source of knowledge. It has almost everything for me. Almost everything.
This forum is better for me than 60% of the books on FreeBSD.
Why? Because I have never seen a book describe bad situations so clearly, colorfully and practically
as on this forum.
The author of a book on FreeBSD is unlikely to write about the shortcomings with such acuteness as here.
Otherwise, it will be an Anti-FreeBSD book.
The book writes about the shortcomings, but they are described very, very poorly.