The only thing of Mamet's I've really liked was the film House of Games. I think Glengarry Glen Ross, for instance, is completely unbelievable. First, I found it impossible to think the characters would have been able to sell an air conditioner in the Mojave Desert. I sensed no real understanding of business in general or the real estate business in particular. This is an "artist's conception" of what the business world is like (which is to say like the "art business" - strictly dog eat dog).