Robert Ludlum, all of them, write the absolute best they can. You can't tone it down. You just do what you do, and if it comes out literary, so be it.
I was going to be the best failed novelist in Paris. That was certainly not the worst thing in the world that one could be.
Graham Greene's work must be included in any survey of top-rank spy novels, and 'Our Man in Havana' may be his best.