Mystery is the PUA. His book "The Mystery Method" is a classic and while some canned routines are dated, the overall theoretical foundation is solid. Perhaps he could have optimised presentation a bit to more easily facilitate inner game and perhaps Bang by Roosh does a better job of presenting game to the average Joe layman by ditching the geeky acronyms and pseudo-evopsych(I love the geeky acronyms and pseudo-evopsych) but overall if you want to understand how dating and seduction works I have yet to see a better book.

I haven't read his newer work (Revelation ect.) but I'd put a high probability on it being quality stuff.