One of my first guides on this subject, and still useful, was an article, "Special Malts for Greater Beer Type Variety" by Prof. Narziss, in the Winter 1993 _Zymurgy_, reprinted from _Brauwelt International_, IV/1991 pp. 284-92. It offers a primer on the modern manufacture and specs of malts including Munich and Melanoidin types among others, sample grain bills, lab analyses of beers, and more in a short, accessible form. (It's the only _Z_ from back in the day I've kept!)
EDIT In the article, Narziss complains that modern Dunkels often have far too strong a roast malt flavor!