Tight Spaces by Lucy Monroe

When a Marine turned special ops agent and a brilliant doctoral student are trapped together in a high-rise apartment, the stakes couldn’t be higher—both for their lives and their hearts.
Danusia is tired of being the odd woman out and when she’s forced to live with Max in her brother’s apartment, she’s ready to act on the intense attraction between them. But after stumbling onto a dangerous secret, she’s now in the crosshairs of people who will stop at nothing to silence her.
Max is tough, stoic, and sworn to keep his distance from Danusia. He’s got five solid reasons he can’t let himself act on the undeniable chemistry between them, and the fact she’s his friend’s baby sister is just one of them.

Will Max break his rules and keep Mia safe… or will their explosive connection be their undoing?