Some time ago, when I was first really getting into Maugham, I was asked which Maugham I would recommend to a new reader. At the time I suggested The Razor's Edge and the stories, especially the Ashenden stories and, if ambitious, Of Human Bondage.
Recently got around to The Moon and Sixpence and have to say this really would be a great starting place for getting into Maugham. It has everything I like in a Maugham novel; a compelling human story that stretches from English drawing rooms and literary society to Paris art haunts and back streets to the South Seas; characters that, like the setting, are invested with authority by Maugham, among them crazed, visionary artists, vulnerable and manipulative women, earthy sailors and rogues, and of course the author himself as narrator and guide; story; language, as only Maugham seems to do it, full not only of narrative and dialogue but observations and insights. For my money, this is a masterpiece of Maugham.