For the books recommendation, I will need to ask DS9 when he is back from school. He is the one reading the books. The complains I heard from him so far are the hard-to-find pieces being used to build some of the projects. It can be disappointing and frustrating if you don't have a replacement piece in your current stash.
For a start, check out this website. The kids will build the project and download the program for it to work. Even though they don't write the program themselves, it is good to see how it is written to make it work.
http://www.nxtprograms.com/index1.html
