As far as good info about SPD in general, I like the suggestions from Portia and blackcat.
Elaine Aron's The Highly Sensitive Child includes a cross-species examination of those who are sensitive their sensory environment. It provides a more gentle and positive view than much of the SPD literature.
About 2e with SPD:
- The Eides' book "The Mislabeled Child" has a chapter on SPD. It's about 40 pages long. While this book is not about 2e kids per se, the Eides specialize in 2e and certainly thoroughly cover the idea that a kid with a problem has huge strengths as well.
- The Twice Exceptional Newsletter has had articles on SPD/gifted 2e. For example: "Living with Sensory Processing Issues: A First-hand Account" by Peter L. Flom (Issue 54: September 2012)
http://www.fcps.edu/cco/prc/newsletter/documents/2e_Newsletter_Issue_54.pdf
