It's hard to decide which of Kosinski's vignette-based novels is the best, since they're all fairly similiar, and passages are interchangeable. There are slight varitations in theme - the protagonist of The Painted Bird is a child, and in Blind Date you have an investor, while in The Devil Tree you have a wealthy young man, but on the whole each one is as good as another. Considering it, though, I think that Cockpit is the best overall, with some of the most interesting vignettes and the most consistently good writing, and one of the stronger protagonists. It's also the only Kosinski book which I can really say shocked me - usually, I'm prepared for the horrible things which his characters do to each other, remembering that it is Kosinski even when things seem to be going well, but there's an episode in Cockpit involving the elderly which took me by surprise. I reccomend this as an introduction to Kosinski's work, or, if you only read one, make it this.