Practically all adaptations of the works of Jules Verne, Edgar Allen Poe, H.G. Wells, and H. P. Lovecraft are pretty appallingly bad, but in most case I think they’re at least trying to be faithful to the source material to some degree.
Some cases where they practically tossed the book away, though, include:
The Mysterious Island (1929) – Well, there’s an island and a submarine, at least. Verne this ain’t
From the Earth to the Moon – not only do they completely change almost everything, but they manage to muck up the science even worse.
Master of the World – actually based more on its prequel, Robur the Conqueror, but I guess they thought the sequel’s title was cooler. The film manages to make a lot of Verne’s book look silly
- The Dunwich Horror* – Effects at the time the original version was made definitely weren’t up to the task, but film was becoming more permissive, so this film doesn’t give us a faithful glimpse of the titular monster, but does give us a glimpse of tits. I really would’ve rather had a shot of Wilbur’s twin brother, all said and done. The remake only had the excuse that it was a low-budget flick.
Die, Monster, Die – wastes Nick adams and Boris Karloff (!!) in a really bad adaptation of Lovecraft’s The Colour Out of Space.
The Raven – Seriously, there’s no way you could adapt Poe’s famous poem into anything but a theatrical short, but they’ve made three – three! – movies with this title. Two of the starred Boris Karloff, as if his presence alone would make a spooky Poe film. The second one, made by Roger Corman, also has Vincent Price, Peter Lorre, and a young Jack Nicholson. It’s a fun pseudo-horror comedy that’s a hoot, as long as you’re not expecting any Poe.
A Connecticut Yankee in King Arthur’s Court – I’ve complained about this many times. There has been a slew of “adaptations” of this, none of which even approximate the real story and none of which have Twain’s wit. Two adaptations were vehicles for stars (Will Rogers and Bing Crosby), most straightforwardly tell you that they’re not doing the real story (“A Kid in King Arthur’s court”). Even the made-for-PBS version throws most of Twain out. I want to see the Destruction of Merlin’s Tower, and the Restoration of the Holy Fountain, and The Boss’ rescue by knights mounted on bicycles. Yes, I know that the Catholic Church doesn’t come out well in the book, and that the end gets grim. I think it can be handled well to avoid pitfalls, and even make the dark ending work.