Enjoyable because it is set in the world of the Dark Tower (plus the art is phenomenal), but not Stephen King. These comics are a sort of filler of the events narrated in Wizard and Glass and the first Dark Tower book. While Gunslinger Born simply retold the events of Wizard for people new to the series, this volume breaks new ground and picks up immediately afterward, narrating events that we only get glimpses of in Wolves of the Calla when Roland relates the rest of his story describing his formative years.
Peter David's narrative is well scripted and follows King's Mid-World conventions and diction, but the plot itself really just bounces around events that we get hints of throughout King's normal story arc-there's really little that could be called new. One of the newer bits of information, and the best part of the story I believe, concerns what happened to poor Sheemie after the events of Wizard, including the source of his mysterious power. There's a lot of potential here, and I hope future storylines develop it.
This volume also shows Roland's mind during his captivation with Maerlyn's Grapefruit, but in my opinion with far less success than the Sheemie story. There's just too much coincidence for my liking (without going into spoiler specifics), in the same vein that the Star Wars prequels contained far too many coincidences that reek of writer's just trying to do what WAS successful before ALL OVER AGAIN and weaving new plot webs between brilliant plot points that are already there-with far less success.
It is clear from reading King's Dark Tower that Roland has no real clear idea of who, or what exactly, the Crimson King is, or his relationship to him. This volume attempts to explain that relationship further, but does so in a way that involves Roland directly. Unless David is planning on giving Roland a massive case of amnesia by the end of the comic series, this storyline simply won't mesh with King's work.
All in all, the story is enjoyable enough though, especially if you're hungry for more Dark Tower and wish it never ended.