Essays. I read 'em online, and now in dead tree form. . . .
All but the last three are discourses on particular things in fantasy fiction, mostly critical. For instance, a leaden style -- the type Ursula K. LeGuin dubbed Poughkeepsie style. ("From Elfland to Poughkeepsie" is mentioned in several.) Names. The characters who blatantly voice the author's opinions. and others. I may quibble about how far he objects to things, but the basic principles are sound.
The last three discuss the history of American fantasy, what Star Wars shows about writing, and use of a logical fallacy in dystopia.
All of them interesting.