I friggin' love Colleen Hoover. 
 I always liked Six and Daniel in the Hopeless series, but this just made them even better. Before we got to see their loyalty and such, but now we get to know them. And I liked them. 
 Not to mention, their love story was beautiful and very sad in a way. 
 Daniel plays a silly boy completely caught up in being just that - a silly boy. Then a girl literally falls into his lap and for a moment, he doesn't act silly. He plays the part of debonair man. However, his charming moment is really just a moment and he doesn't see the girl again. A year passes and he finally decides to end his horrid relationship with some uber bitch. Sky, his best friend's girlfriend, introduces him to her best friend. Shortly after the introduction, he's told to stay away from her. 
 Wrong move. 
 Daniel immediately sets out to make her his - mostly for the challenge. Little does he know that Six just happens to be perfect for him. 
 (view spoiler)[Got to admit, I was shellshocked over the pregnancy thing. I did NOT see that coming. (hide spoiler)] 
 This was such a great addition to the Hopeless family and I'm astonished she gave it away for free. Just makes me love Colleen Hoover even more. 
 I understand that this can be read separately, but I highly recommend reading Hopeless and Losing Hope beforehand. Understanding Sky and Holder, I think, is key to understanding their best friends.