Of course, it's also a lot more explicitly bigoted and homophobic than the movie, so there's that too. Get through that stuff and you've got a superior hard-boiled detective novel, one which had a psychological and stylistic depth that would influence hard-boiled fiction ever after.
This is the first novel-length adventure of Chandler's Philip Marlowe, the Los Angeles PI with a heart of gold. Well, gold alloyed with cynicism and pithy, pungent comments on The Way Things Are. Chandler's Marlowe arrives here pretty much entirely formed. He'll stay on a case if he thinks justice needs to be done, regardless of what a client wants. He likes chess, whiskey, and pondering the dusty nature of his office.
The written word in America 1939 had a bit more freedom than Hollywood movies in 1946, so certain portions of the plot are simply a bit more explicit when it comes to the pornography ring that drives part of the action. This also leads to the bigotry and homophobia becoming more explicit -- Bogart couldn't utter the opinion that "a pansy has no iron in his bones" in a movie, but Marlowe sure can, and does, in the novel. Hoo ha!
Nonetheless, the novel still reads with a surprising amount of stylistic freshness. Chandler was not better than all those who would follow him into the hardboiled world he remade, but he certainly was better than most -- and better than Dashiell Hammett, who was the epitome of the hardboiled writer before Chandler. Highly recommended.