Cocksure (Cocksure #1) by K.I. Lynn and Olivia Kelley

Niko

My life is great. I love my job, have awesome friends, and a great family. 
Women love me, even if they know it’s just for a night.
I always thought love at first sight was bullshit. Then she came storming into my life.
She tore through my every rule, rocked my world, and knocked me on my ass.
There’s only one problem...she lied.
Turns out my best friends little sister isn’t so little anymore.

Everly

I stole a night with my fantasy. Lied to him.
After ten years of not seeing each other, Niko doesn’t even recognize me.
So I take what I want from him, what I need from him. Without worry. Without consequence.
What I didn’t count on was the lingering need for him. 
What I chose to forget is that he is my brother’s best friend.
Once the truth is out, the game changes. There are consequences.
I should have known nothing in my life is ever simple.

ellie's $0.02:

I've never been so sure about a cock in my life.

K.I. and Olivia bring a little of everything in Cocksure.  It was fun at times, emotional at times, and infuriating at times. 

Surprisingly Everly was the one I wanted to kill more than the cocky Niko.  The characters had their faults which is always refreshing for a cocky fellow.  K.I. and Olivia did an amazing job of showing multi-faceted and faulted characters.  Niko and Everly both had their moments of shining and... not.

This duo wrote seamlessly together with the dual POV of the characters.  A little dirtiness, a little sexiness, a little romance, and a little reality.   And just when I was frustrated with a situation or one of the characters and wanting to punch the wall, I pushed on and the characters would rectify themselves before I kicked their rectums.  It ain't a short book or tale... it took me the full spectrum and then some.

This is a solid winner about a wiener.