WOW!!! What a fascinating, twisty, surprising story!! I love KA Tucker's writing so I was very excited to read this one and it is VERY different from her other books. Adult, suspenseful, thrilling...with an ending that I never saw coming! This is one of those books that you will not put down until you are finished. It is told in flashbacks and in alternating POV's from Maggie and her best friend Celine's diary entries. Maggie does not believe her best friend committed suicide and begins investigating the circumstances surrounding Celine's death in New York City. She meets is all of the important people in Celine's life, including Jace, who may or may not be hiding something. There is also Grady, the very sexy building super, who is also under suspicion in Maggie's eyes. 
 I gingerly unfold the paper that's obviously been handled many times, judging by the crinkles in it. 
 My eyes widen. 
 A naked man fills one side. He's entrancingly handsome... lying on his back, one muscular arm disappearing into the pillow beneath his head, a white sheet tangled around his legs, not quite covering the goods... 
 Who the hell is this guy and why didn't I ever hear about him? And where is he now? Where were they together last? 
 Does he know that she's dead? 
 ... I slowly fold the paper back up. Celine's cursive scrawl decorates the back side in purple ink. Words I hadn't noticed before. 
 Words that make my heart stop now. 
 'This man was once my salvation. Now he will be my ruin.' 
 Maggie and Celine were childhood friends but grew apart once they got older. Maggie learns many things about Celine's life through reading her diaries and is convinced that the diaries will be the key to learning about her death. He Will Be my Ruin is a tightly written, taught suspense thriller that has a completely resolved ending and a smart, resourceful heroine. There's plenty of twists and turns to satisfy even the most jaded mystery reader. I loved this book and hope that KA Tucker writes more suspense in the future!! 
 (ARC provided by the publisher in return for an honest review.)