Read about 25-30 of his books. The Dark Tower VII is the definite favourite, others are Duma Key, 11/22/63 and maybe The Stand (which might be a bit dated). I don't think he writes too long books at all. I mean, I've never found the extra length of some books to be negative. Quite the opposite in some cases. Spending time with characters while the plot takes the backseat for a while isn't necessarily bad - not when they're as good as King's. Whereas someone like GRRM just repeats the same prose over and over, King actually never feels repetitive - unless maybe we're talking about his typical protagonists who usually end up being a version of himself (teacher/writer, addict, cripple - later years). Sometimes I'm disappointed - I didn't get Carrie or It at all - but most of he time he's at least very readable (Doctor Sleep, Mr Mercedes, The Dead Zone all fall into this category).