Two more possibilities:

To continue with Ryk Spoor's books, Princess Holy Aura is his take on the magical girl warrior genre, which has lots of similarities with the superhero genre. Has a good mix of superpowered action and character drama. (Though one of the best and most tense action scenes is nearly entirely mundane.)

Then you have The Annihilation Score by Charles Stross. This is more of a superhero story mixed with more than a fair bit of horror. It's part of his Laundry Files series, but it should be a decent intro point, and reasonably standalone. Mo O'Brien gets bureaucratically assigned to lead a team of newly emerged superheroically endowed individuals, newly sworn in as auxiliary police officers.