Most of those who have seen I, Monster review it fairly mediocrely. In fact, I, Monster is an extremely good version of Dr Jekyll and Mr Hyde. Most interesting of the changes it rings up is to take the story directly into the realms of Freudian psychology. Other versions, like the 1941 adaptation, had dealt with Freudian psychology, but not particularly well. Here, instead of a drug that unleashes the beast within, Jekyll/Marlowe has created a drug that dissolves the superego. Some of the films most fascinating scenes are ones early on where an uptight girl, after taking the drug, strips her clothes off and offers herself to Christopher Lee, or where an angry businessman is turned into a crying child.
I, Monster was originally filmed in 3-D, which means there are a few gimmicky shots of Christopher Lee waving Bunsen Burners or holding squealing mice up into the camera. The film is made with some surprisingly good period sets. Christopher Lee gives a good performance as Jekyll/Hyde, a role he also essayed in Hammers The Two Faces of Dr Jekyll (1960). He is just the right actor to portray the cold and tightly repressed Marlowe and makes an effective change between that and the lascivious Blake. The transformation is conducted without much makeup and is believable.
Director Stephen Weeks was a minor director on the outskirts of the English horror scene where he also made the likes of Gawain and the Green Knight (1973), Ghost Story (1974) and Sword of the Valiant: The Legend of Sir Gawain and the Green Knight (1983). Producers Milton Subotsky and Max J. Rosenberg and their Amicus production company were, next to Hammer Films, the most successful English horror-producing company of the 1960s and 70s, making a number of psycho-thrillers, several sf films and gaining their greatest fame with a host of horror anthologies beginning with Dr Terrors House of Horrors (1964).
Other versions of Dr Jekyll and Mr Hyde are: Dr Jekyll and Mr Hyde (1908); Dr Jekyll and Mr Hyde (1910) with Alvin Neuss; Dr Jekyll and Mr Hyde (1912) with James Cruze; Dr Jekyll and Mr Hyde (1913) with King Baggott; Dr. Jekyll and Mr. Hyde (1920) with John Barrymore; Dr Jekyll and Mr Hyde (1920) with Sheldon Lewis; Dr Jekyll and Mr Hyde (1920) with Sheldon Lewis; Der Januskopf (1920), a lost German version with Conrad Veidt; the classic Dr. Jekyll and Mr. Hyde (1931) with Frederic March; Dr Jekyll and Mr Hyde (1941) with Spencer Tracy; Jean Renoirs The Testament of Dr Cordelier (1959) with Jean-Louis Barrault; The Two Faces of Dr Jekyll (1960), the Hammer version with Christopher Lee; Dr Jekyll and Mr Hyde (tv movie, 1968) with Jack Palance; The Man with Two Heads (1972) with Denis DeMarne; Dr Jekyll and Mr Hyde (tv movie, 1973), a musical version with Kirk Douglas; Walerian Borowczyks Dr Jekyll and His Women (1981) with Udo Kier; Dr Jekyll and Mr Hyde (tv movie, 1981) with David Hemmings; a 1985 Russian adaptation starring Innokenti Smoktonovsky; Edge of Sanity (1989) with Anthony Perkins; The Strange Case of Dr Jekyll and Mr Hyde an episode of the tv series Nightmare Classics (1989) with Anthony Andrews; Jekyll and Hyde (tv movie, 1990) with Michael Caine; My Name is Shadow (1996), a Spanish version starring Eric Gendron; a bizarre tv pilot Dr Jekyll and Mr Hyde (1999), which combined the story with Hong Kong martial arts and featured Adam Baldwin playing a Jekyll as a superhero in the Orient; Jekyll & Hyde: The Musical (2001) with David Hasselhoff; Dr Jekyll and Mr Hyde (2002) directed by and starring Mark Redfield; the excellent British tv reinterpretation Dr Jekyll & Mr Hyde (2002) with John Hannah; The Dr. Jekyll and Mr. Hyde RocknRoll Musical (2003) with Alan Bernhoft; the modernised Jekyll + Hyde (2006) with Bryan Fisher; The Strange Case of Dr. Jekyll and Mr. Hyde (2006) with Tony Todd; the modernised BBC tv series Jekyll (2007) with James Nesbitt; Jekyll (2007) starring Matt Keeslar where Hyde becomes a virtual creation; and the modernised Dr. Jekyll and Mr Hyde (2008) starring Dougray Scott.
Other variations include the would-be sequels Son of Dr Jekyll (1951), Daughter of Dr Jekyll (1957) and Dr Jekyll and the Wolfman (1972); the comedy variations Abbott and Costello Meet Dr Jekyll and Mr Hyde (1953), The Ugly Duckling (1959), the Italian My Friend, Dr Jekyll (1960) and The Nutty Professor (1963); versions where Dr Jekyll turns into a woman with Dr Jekyll and Sister Hyde (1971), the Italian comedy Dr Jekyll and the Gentle Lady (1971) and Dr Jekyll and Ms Hyde (1995); a Looney Tunes cartoon Dr Jekylls Hide (1954) where Sylvester the Cat transforms into a dog after taking the formula; the erotic/adult versions The Naughty Dr. Jekyll (1973), The Erotic Dr Jekyll (1976), Jekyll and Hyde (2000), Dr. Jekyll & Mistress Hyde (2003) and Jacqueline Hyde (2005); Dr Black and Mr Hyde (1976), a Blaxploitation version where Jekyll is a Black man who turns into a white-skinned monster; the amusing send-up Jekyll and Hyde ... Together Again (1982); a wacky childrens tv series Julia Jekyll and Harriet Hyde (1995); Killer Bash (1996) set in a frat house with an avenging female Jekyll; and the excellent deconstruction Mary Reilly (1996), which tells the story from the point-of-view of Jekylls maid. Dr Jekyll appears as a character in The League of Extraordinary Gentlemen (2003) played by Jason Flemyng and in the tv series Penny Dreadful (2014-6) played by Shazad Latif, which both feature team-ups between characters from Victorian fiction, while the animated The Pagemaster (1994) features a Dr Jekyll voiced by Leonard Nimoy.
Full film available online here:-