God of Fury by Rina Kent ((Legacy of Gods #5):

From USA Today bestselling author Rina Kent comes a new STANDALONE MM college romance.

I’m not attracted to men.
Or so I thought before I slammed into Nikolai Sokolov.
A mafia heir, a notorious bastard, and a violent monster.
An ill-fated meeting puts me in his path.
And just like that, he has his sights set on me.
A quiet artist, a golden boy, and his enemy’s twin brother.
He doesn’t seem to care that the odds are stacked against us.
In fact, he sets out to break my steel-like control and blur my limits.
I thought my biggest worry was being noticed by Nikolai.
I’m learning the hard way that being wanted by this beautiful nightmare is much worse.

This book can be read on its own, but for a better understanding of the world, you might want to start with God of Malice.