If my math is right Stephen King hasn't written a screenplay since 1992's Sleepwalkers (I'm talking movies here, not TV things), so A Good Marriage is notable for returning the pen of King to the screen. We have been seeing fewer wide-release King adaptations in general, with much of his work getting adapted for TV or going mostly straight to video.
Based on a novella in his recent Full Dark, No Stars collection, A Good Marriage has Joan Allen discovering her longtime, perfect husband is actually a serial killer. What happens then, according to the trailer, is the stuff of basic cable TV movies; this trailer makes the movie look disappointingly small and cheap. I think 90s thrillers are coming back, which is too bad because they really sucked the first time around.
This has such a good premise, too. Maybe the actual film is better than the trailer. The poster is certainly great: