Son of Frankenstein is unusual because it maintains its quality despite being the third film in a series, and despite a change in directors. While Roland V. Lee was hardly in the league of predecessor James Whale, he was an above average director who could do good work with the proper material and resources. Here he has a strong story, fine inherited production motifs, and an excellent cast that includes Basil Rathbone, Bela Lugosi, Lionel Atwill, Josephine Hutchinson, and Boris Karloff, in his final movie performance as the Monster. The film established several motifs that would later be used in similar films -- for example, the initially uninterested son who gradually becomes obsessed with the work of his mad-scientist father. Mel Brooks fans will instantly recognize the story line of Young Frankenstein (1974), which borrowed several other bits of this film, including a delightful satire of Atwill's stiff-armed performance. Son of Frankenstein is a step down from the expressionistic heights of Whale's Frankenstein and The Bride of Frankenstein, but the step is not so great as to leave the film without its own substantial merits.
by Richard Gilliam review