The problem is that there is a very different technique to writing prose fiction, especially a novel and a comic book story.  the latter is more akin to a short story and even comic book epics aren't the equivalent of a novel.  A novel lets you explore all kinds of facets of a story, while comics have some limitations.  By the same token, comics are also primarily visual storytelling and can use an illustration to make a point that paragraphs might be required, in prose.

In general, very few comic book writers have proven to be successful as novelists or prose writers, in general; at least, from the fan generations.  Earlier generations had guys like Gardner Fox and Edmond Hamilton, Otto Binder and a couple of others who dabbled in prose and comics.  Many proved more successful in writing similar material, like episodic television.

Trying to tell a comic book story...or, rather, a superhero story, in prose, is difficult because of the visual nature to so much of it.  The ones who have done it well are few and the biggest, in my eyes is Elliot Maggin.  He was one of the best Superman writers of the 70s and he translated him perfectly to the two novels he wrote, to be marketed alongside (but not adapting) the first two Christopher Reeve films.  He would later be tapped to adapt Kingdom Come to prose and he utilized the format to explore some things that the mini-series didn't have room for.

I tried the various batman novels and anthologies that came out in the wake of the Burton movies and they were mostly mediocre, at bewst.  i think I enjoyed only two stories from the anthologies, to any great degree.  I didn't read some of the later 90s/2000s items, because of the track record.  On the Marvel side, I read Otto Binder's Avengers:  Battle of the earth-Wrecker and it was just "okay."  Same with Captain America:  The Great Gold Steal, by Ted White.  I read the Marvel Super Heroes anthology, with the Shooter Avengers story, a Claremont X-Men and a Daredevil and a Hulk story.  None of them were particularly great and the Avengers one kind of rehashed a comic book storyline.  The X-Men one sort of did, too.  Didn't read any of the rest.  Did not read Diane Duane's Spider-Man books, but did read Peter David's Hulk novel.  He understood the difference in mechanics, given his Star Trek work; but, the mini-with George Perez added a lot that the book couldn't convey.  have not read Greg Cox' Iron Man; but have read his Khan novels, for Star Trek.  I did read Tony Isabella's Captain America:  Liberty's Torch, which was okay, but didn't convey the action well and Will Murray's Nick Fury, Agent of SHIELD:  Empyre was a disappointment to me, but more for the threat and how SHIELD was handled.  I wanted something more Steranko.

I just don't think superheroes work very well in prose format, because there are too many visual elements built into them.  Now, where Maggin succeeded with Superman, aside from giving him a more rounded personality and more adult motivations and emotions, was in how Superman attacked a crisis.  Maggin was able to present the mental strategy that Superman applied to the problem and illustrated the creative ways he used his abilities.  The first novel has a sequence where Luthor sends out a bunch of men, in backpack helicopters, to launch simultaneous bank robberies, on the financial sector of Metropolis.  He details how Superman deals with the threat in multiple locations.  He does things like fuse the door locks on a roof access and then dumps some of the crooks onto those roofs.  He creates an updraft to alter the course of some others, while he deals with another crook, to put them out of play until he can return and collect them.  In another section, he deals with a massive tsunami and applies multiple strategies to lessen the impact.  He creates a trench on the ocean floor, to divert a certain volume of the wave.  He plunges into the wave to create a vacuum to draw away another portion.  he vaporizes some of it and uses his super-breath to divert it over a drought area to then provide rain and dispose of more.  The sum total of his actions lessons the wave that finally hits the shore to that of a heavy storm, but far less than a hurricane or tsunami, mitigating much of its impact and danger.