stephen king for a 13 year old?

My 13 year old grandson is an avid reader and very intelligent and mature in some ways ( though not yet gone through puberty) . He wants to read Stephen King books and although neither I nor his parents have read any we are a little wary. Obviously if he finds them too scary he will stop but can anyone who reads these advice on any to read or not to read. Are any of the contents "adult" themed and/or likely to warp or corrupt him for life! There is so much unsuitable stuff of all sorts available to kids nowadays and they cannot be sheltered but I do want him to be a fine young man!