You may be selling it short just to be on the safe side. I'd consider their previous two features remarkable disappointments so this is certainly better. Of course I always believe a film should stand on its own and it makes no difference whether its based on a book or even a real event. Jokingly Blood Simple and Fargo were based on true stories which people were quick to find out was a lie. This film comments on it when Tommy Lee Jones is reading the paper and says "You can't make that stuff up".