The first of four Bogart-Bacall films, it's also possibly the best. Bacall was a model discovered by Howard Hawks, and she and Bogart began a passionate off-screen affair that ended in a magnetic marriage. You can tell. The screen sizzles, and Bacall has an extraordinary wit and charisma - especially given her lack of experience at the time. Apparently her "look" (a jaguar-stare up from under lowered eyebrows) originated from her attempts to keep her chin steady when she was trembling from nervousness in her début scene.
Bacall didn't make very many films, and arguably none as good as this - the script zings and the plot is suspenseful if a trifle inevitable. You should go and see it if you like witty film noir or if you have any interest in seeing the birth of one of the most unusual and stylish film stars of the century.