I taught music theory for 8 years, and we used Laitz. It's a solid textbook. The book I learned from myself was Walter Piston (!) which is extremely old-fashioned, but unlike Laitz, Piston worked from a defined 'canon' of classical music within which his theory was consistent. Laitz tries to incorporate many different kinds of music, and then he often reaches quite simplistic conclusions. Kostka and Payne is absolutely fine, though, if you want to know 'enough' and the pedagogical style is excellent.