Dell's One Shot series regularly published book-length stories in their adventure (i.e. not funny-animal) books. Of course movie adaptations were full-length. Dell's novel adaptations also tended to be book-length, for example their Luke Short and Zane Grey adaptations. Books with continuing characters were more likely to have two stories per issue, but in late 40s and early 50s Dells they frequently got long stories. A random example is O.S. 269, Johnny Mack Brown. Johnny gets a full 48 pages to strut his stuff. The stories often continued over the inside back and back covers. You were out of luck if you got a coverless copy.
After Western Publishing and Dell Comics split around 1962, Dell published numerous full-length stories. These included both licensed TV characters like Cain's Hundred or Follow the Sun and their original characters, including Kona, Monarch of Monster Isle and Space Man.
When a title was offered by subscription postal regulations required more than a single story if the publisher wanted the cheaper second-class mailing privileges. That meant an issue was either split between two stories featuring the lead character or a long lead story and a shorter backup feature. Text stories were included because postal regulations also demanded that second-class mail magazines have some text, not just comics.
Give Dell a look-see. You might find some books that appeal to you.
