Check out "Tourette Syndrome and Human Behavior" by David Comings, M.D. It is a huge thick book with extensive research on the genetics of Tourette Syndrome and other related disorders. I am still wading through it but i am learning so much. It was relatively inexpensive to buy a decent copy, used, on Amazon. My kids represent dyslexia, Tourettes, and HFA, all genetically related according to Dr. Comings' research. This book is full of tables, graphs, and data; also the explanations thereof for the layperson. Rather technical but pretty readable. It was published in 1990 so some of the areas have much more extensive research available by now. But the information is not obsolete by any means.