There are several good books on the market, but as Jesse just said, I have found much more reliable info on this site than the shelf of books sitting by my side now. The people with the expertise are on here, most show up every day. I'll not go into trying to name any of them because I know I would leave out some of the best. Read the post here and in the forums of intrest to you, check out the library index at the top right of the home page and if the info needed is not found there, then post your question. You will receive many excellent answers.
I just fell onto this site a few months back and have learned more about, not just pen turning, but turning in general than I did in the previous two years with books and personal mistakes. You will find many vendors offering some of the best material anywhere here also. Just my $0.02.
Charles