Partyboy13, David_A_Whitehead, and The1complainer are all exactly on track, Mark_v (and just look at all that typing The1complainer did for you!).
This topic has been broached before; see the sticky at the top of the Mentalism section. Or just click here:
http://www.penguinmagic.com/discuss/vie ... hp?t=43647
With that said, in mentalism the name of the game is books. Usually old books. So if you don't like to read books, mentalism probably isn't for you.
But if the books you need aren't on the Penguin site, that doesn't necessarily mean that you have to shop elsewhere.
Call or email the folks at Penguin. If you tell them what books you'd like, they can probably special order them for you. And if enough other people ask for them too, I'd be surprised if they didn't start carrying these titles on a regular basis.
Phone: (702) 734-3333
Go ahead. Call or email Penguin. You'll get the books you want so you'll be happy; the folks at Penguin will make more sales, so they'll be happy; and Penguin Magic will ultimately become a better store for mentalists and mental magicians, so we will all be happy.