My definition of a novel is getting a bit loose but I have to recommend this terrific collection of bizarre short stories. His odd sense of humor and darkly comic stories have been adapted into Alfred Hitchcock Presents episodes, so that should be an indication of what to expect.
"Evening Primrose" is the first story I read of his and I instantly fell in love. You will, too!
Fun fact: Seek out the LP recording of Vincent Price reading two of Collier's stories, including "Primrose". The perfect combination!
Copies can be found on Amazon.