My all-time Must Be Made Into A Movie Science Fiction novel is Randall Garrett's Too Many Magicians. Set in an alternate Present which springs from two assumptions:
1. Richard the Lion Hearted did not die overseas, but returned to England to rule for another 20+ years and so the Plantagenet dynasty still rules The United Kingdom of Britain, France, and New England (which is everything from Canada to Panama) at the current time, which is 1965 when the novel was written.
2. Back in the 13th - 14th century, some scribbling monk discovered the mathematical laws that govern magic, putting 'thaumaturgy' on an experimental and provable basis, so that magic takes the place of a great deal of technology.
The result is what we now call 'Steampunk' but much, much better realized.
For instance, the lead character, Lord Darcy of Rouen, Chief Investigator for the Duke of Normandy (the current King's brother) has no magical talent whatsoever, but is a pure Sherlock Holmes deductive reasoning detective. His assistant is Sean O'Lachlain, a Forensic Sorcerer. The mystery at the heart of the story is that the Chief Forensic Sorcerer for the city of London is murdered in his locked-from-the-inside hotel room at a convention of all the greatest magicians in the Empire. He is stabbed through the heart, but a sorcerous examination of the crime scene indicates that he was killed a half hour before he died, no one else was in the room at either time, and magic was not used to kill him.
It has it all: a Sherlock Holmes story with magic, spies, CSI, a locked room murder mystery and a superb integration of Science-Fiction/Fantasy elements into a Victorian background.
Oh, and a Stephen Hawking-like character, a non-magic-talented theorist who investigates the most obscure elements of Theoretical Thaumaturgical Mathematics.
And a Polish spy ring, a British Naval Intelligence secret agent, and an Aztec Apprentice Magician named Lord John Quetzalcoatl.
Like I said, it has everything...