Among my favorite film books is Michael J. Weldon's two-volume "Psychotronic" film guide. The first was published in 1983 and the second in 1996 (Michael hopes to publish a third at some point). Unlike Leonard Maltin's annual book, Weldon doesn't update an existing guide; each new guide is an entirely new volume. If you want to read about Halloween, you need Vol. 1 and if you want to read about Halloween 4, you need Vol. 2. A "Psychotronic" movie can be fairly easy to define. It's basically any of the "lower" film genres, dealing with the more questionable elements of society: horror, sci-fi, bikers, strippers, superheroes, zombies, kung-fu, vampires, comic books, drugs, sex, action heroes, rock 'n' roll, midnight movies, monsters, witches, cults, serial killers, magic, time travel, robberies, heists, contract killers, gladiators, Spaghetti Westerns, mad scientists, murder mysteries, pimps, voyeurs, etc.