What makes it work so well? I'll say the success rests on a combination of three things: the infectious chemistry between the two leads Elliot Gould (in a hilarious role) and George Seagal the fully realized world Altman creates for his characters and that overall the movie is capable of both belly-laughs and profound sadness but it is always subtle, never says anything more than it has to, leaving just enough for the viewer to participate. Sure this is not the first movie to be made about the compulsiveness of gambling and people trying to find meaning and pleasure in empty addictions but it is such a fresh and enjoyable movie one has to sit down and take notice. It's the handling of the subject matter that makes the difference.
It is Altman the auteur in top form, his quirks and distinctive traits that separate him from all directors of his time emblazoned over every minute of this delightful mixture of comedy and drama. It's surprising how little known California Split is but even in a career filled with great movies such as Robert Altman's it deserves more recognition.