I'm no lawyer, but it looks about as legal as the original Napster (which is to say, not).
I see books there that are still in print and most likely under copyright.
The grammatical errors lead me to believe that this is an offshore operation (or someone that never graduated from grade school).
Remember that most of what we are doing and what we work with is old technology. The book "how to run a lathe" is still appropriate, even though it predates most of us. Old books that are out of copyright are great.
You can search on older books that are out of copyright at:
and select the "full view" or "public domain" options.
Search on the author "Fred Colvin" and you can get a lot of stuff and then download it as PDF to your computer.