Calling Chaos by Grae Bryan

Cooper didn’t mean to summon a demon. He may be a hacker for the Mafia, but he’s not exactly brave or adventurous by nature. He was only trying to do a small, easy job for his terrifying boss and then get back to not leaving the house for days on end. Only now that the demon’s here, promising to be Cooper’s friend for as long as he needs one, Cooper might just be lonely enough to let him.
Chaos knew it was finally his time to get summoned. No more being stuck in the boring Void, no more hanging out with the same three dull demons. It’s time for madness and mayhem and answering to no one but himself. Except Chaos doesn’t expect his newest summoner to be quite so…timid. And sweet. And willing to cater to every single one of Chaos’s many wants and whims. Maybe it wouldn’t hurt to stick around for an eternity or two.
Now Chaos just needs to convince his new friend that it really isn’t all that scary to be mated to a demon, even one who loves to play with fire.