I read this story as a Kindle book, I think about ten years ago. It's probably in my library if I search enough, but I'm putting down details while I remember them.
The protagonist (a journalist by profession, I think) has had a fascination with superheroes since he was a child, when a very prominent Supermanalogue (who I think has a lion theme to his costume, maybe also his name) saved him from a fire (I think I remember him flashing back to hiding in a bathtub with flames around him when the superhero shows up). While in another town (I'm pretty sure a large city in the United States), a fight happens nearby him and something happens (I think he blacks out in the process of it) and when he wakes up, he sees the superhero or supervillain acting out of character while they think he's still unconscious. Shortly thereafter, he learns he has a superpower, I think to duplicate the powers of another person near him, and he's brought in on the secret, which is that all of the heroes and villains in town are employed by one guy, who arranges for their fights with the idea being that staged fights control the damage, and also discourage regular criminals, who assume they won't be able to compete with the supervillains. People are partly cast for how scary their powers are, but some switch their roles (and costumes and names) according to what's needed. The main character has a romantic interest (who, I think, was playing the villain in that first encounter), and he makes friends with some of the other supers. Ones I remember:
- There was a "blob" guy who wasn't very intelligent (largely spoke his name), but could take the appearance of anyone else and was largely indestructible. He was sometimes used as a "stunt double" for supers who had to undergo something normally destructive.
- One of his teammates could take on animal powers, but only ones matching these little charms he carves (I think he had an aboriginal background, and credited his powers to that)
- Another guy had no power other than to broadcast music that everyone in the area could hear. He's apparently often snuck onto the scene to provide theme music.
- There's a martial artist who can summon up to four duplicates of himself who is later revealed to be five people who all have the power to teleport to each other, so they all wear the same costume and claim to be a duplicator
- I think that the boyfriend of the girl he's crushing on (who plays a hero but isn't nice) is some sort of gravity manipulator
As he progresses in the organization, he realizes that there's something not right going on in the group, I think involving people having bouts of amnesia and fugue states. At first, he suspects either the manager or the romantic interest's boyfriend, but eventually he finds that it's
The blob guy, or someone closely related to him, who has the ability to steal powers, and might actually be an extraterrestrial being.
It also turns out that the main character finds that his powers actually stem from the hero who saved him at the beginning, and that they're more powerful than he thought (I think something along the lines of that he gets complete understanding of the power when he gains it, knowing things to do with it that the original could not).
I think the author wrote a prequel book, which focused on the rise of the superhero who saved the first book's protagonist as a child as he deals a super who is eliminating all of his possible competition. I think there were also a number of short stories sold as 99-cent books on Kindle, including one where the protagonist has to give a speech in the aftermath of having defeated the villain in the first book and another where they have to deal with the ghosts of dead heroes.