All these suggestions are great, to add to the pile, I think one of the strongest things you can do when getting into mentalism is to WATCH, not just read.
Youtube is a fantastic resource for this kind of stuff, type into the search bar things like; mentalist, mind reader, psychic and anything else that you feel relates to the subject.
Just like an actor training for his latest role, it's worth seeing what else is out there and what the people that are 'real' look like when they are demonstrating their skills. From there, it's just a hop, skip and a jump to form your own interpretation. You'll find qualities that you like and qualities that you dislike in all the performances, so write a quick list of these and you'll have in front of you a rough character profile!
Good luck!