I'm biased towards this book because I wrote some of it, but I still
think it's the best book out there for advanced Mindstorms users.
If you feel that the RCX-Code environment hems you in and you want to
explore alternative software like NQC, pbForth, or legOS, then this book
is for you.
If you want to learn more about how the sensors work and perhaps try
your hand at making sensors, the section by Mike Gasperi is a goldmine of
information
Ben has put together a delightful book that will help parents and
teachers to work together with children to build interesting robots
with Mindstorms.
The effort that Ben has put into making the projects accessible
to children shows. With full color illustrations on almost every page,
stories from children, and kid-friendly projects, this is one resource
you can't do without.