I just recently read a really great erotic book titled Aqua Erotica: 18 Stories for a Steamy Bathby Mary Anne Mohanraj. It has sexy stories all centered around water.  The book is waterproof and intended to be read in the bath tub, but can be read at any time.   The stories are short and very sensual.  I think this could be a perfect book for someone who has never read erotica before, the bathtub is a perfect time for one to start to explore their sexuality.  You are usually alone, relaxed and able to let your mind escape. I highly recommend this book.