The Boyfriend Effect (Frisky Business Book 1) by Kendall Ryan

A sexy new brother's best friend romance from New York Times bestselling author Kendall Ryan.
I’m not boyfriend material. If a trail of broken hearts and a piss-poor record of failed relationships have taught me anything, it’s this.
My buddies are happy to give me shit about my latest breakup from here to next Sunday. Thanks, but I’d rather have a root canal. And a vasectomy. At the same time.
Relief comes in an unlikely package—the gorgeous and feisty Maren. She just so happens to be my best friend’s sister, so that’s not awkward at all. But I’m a man on a mission, and Maren is down to teach me all the ways I’ve been failing as a boyfriend. Apparently, there are many. And it’s all very informative—until I start to catch feelings.
Now it’s not just my reputation on the line, but my heart too.