According to Amazon, there is a new version of Paul Wellin's book out in early 2016.
I would also add Cliff Hastings, Kelvin Mischo, and Michael Morrison's Book: Hands-on start to Wolfram Mathematica. There is a key in the back that gets neat stuff like a free on-line course ($50 value), so the book pays for itself.
I have seen Stephen's book in pre-release format, and started to read the on-line version. It takes a different approach from either these books, and is worth while just for the pedagogy.