I don’t think Evil of Frankenstein deserves quite as much venom as is sometimes flung its way. It’s a misstep, sure, and a disappointing experiment, sort of like one of the doctor’s many unsuccessful attempts at breathing life into the dead.
For my money, the double whammy of Curse of Frankenstein and Revenge of Frankenstein represents the high water mark for Hammer horror productions. They’re simply wonderful films, perfectly connected to one another without the sequel being a derivative rehash.
Hammer rushed out two more horror-scifi amalgamations, then in 1956 went to work on what was to be their first in a series of films that were, depending on who you are, either adaptations of classic works of British gothic horror, or remakes of old Universal Pictures horror films.