Castle of Frankenstein was the brainchild of Calvin T. Beck, remembered today largely for the rumor that he might have been the inspiration for Norman Bates, the momma's-boy murderer in Robert Bloch's novel Psycho. Beck had a background in publishing within Joe Weider's small empire of health magazines, and in 1969 parlayed his experience into a one-shot self-published effort, Journal Of Frankenstein. Three years later he returned with a tweak to the title and more determined to succeed.
Famous Monsters of Filmland was a pretty good magazine when you were ten, but eventually a kid starts to grow up and wants something meatier. Castle of Frankenstein filled that void, with solid articles on a variety of related topics. The magazine didn't just include coverage of monster films, but all sorts of fantasy and science fiction movies as well (one issue even featured an interview with Alejandro Jodorowski), B-movies, and comic books.
Unfortunately, the magazine wasn't quite high enough on owner Beck's list of priorities, and although his stalwart editors (fan-professionals like Larry Ivie and Bhob Stewart) put forth a heroic effort, the frequency of issues was so hit-or-miss that fans despaired of ever finding a new issue on the racks; witness the fact that only 26 issues were released in 13 years. Beck eventually shelved the project in 1975 to devote more time to writing and editing books (such as Heroes of the Horrors, published that year) and fandom mourned.