Looking for a good text on science of grilling and barbecue
Although it isn't extremely detailed, there is some good information on this topic in Nathan Myrhvold's Modernist Cuisine: Vol. 2 Pages 7-17 are dedicated to grilling and there is some relevant information in the sections on smoking in both Vol. 2 and Vol. 3 as well.

Harold McGee's food science classic On Food and Cooking has most of the information on this topic that can be found in Myrhvold's tome at significantly less cost.  Most of the information specifically about wood and flavor production can be found at the end of chapter 8 "Flavorings from Plants"