2.5 stars 
 Oh hello, handsome man with scruffy face! Nice to see you. Yes, the cover totally drew me in. Then I read the blurb and it was appealing so I requested the book. And then it sat collecting dust on my Kindle, waiting for me to dust it off and read it. When COYER rolled around, I decided to dust it and read it. 
 I like gargoyles, I even have some in my living room so I am a sucker for books with gargoyles. Add in some romance and mystery and this should have been a sure win. Should have been. "Heart of Stone" has potential. The set up of Guardians (gargoyles), Wardens (magicians), and nocturnis (basically, the bad guys) is interesting and Warren has put some thought into it. But the story itself is weak. 
 Ella (and I do like that name!) has a dark and dangerous power inside her that she can't control and tries to keep bottled up. At a museum event, she's nearly raped and she plays the helpless damsel to perfection. Oh, she does hit him and then regrets hurting him, it wasn't nice of her. :( *smacks Ella* Really Ella? REALLY? Grow a spine or a set of balls or SOMETHING. Anyway, after her boss escorts the would-be rapist off the premises, Ella goes and pouts to her favorite gargoyle statue. She's then almost attacked by an assassin, well, someone with a knife, and the gargoyle comes to life. After he saves her, she goes into shock, and her power bursts forth and attacks the gargoyle. Umm, OK. She's almost raped, almost killed, but it's only when she's saved that her power comes out and it attacks her savior? Ooookay. 
 So, Ella is both irritated by Kees, the gargoyle, and attracted to him. She whines, sulks, and pouts, and occasionally, oh so occasionally!, shows some spunk and sass. Kees himself is condescending, patronizing, and stubborn. His favorite nickname for her is "Little Human"; yeah that's not condescending at all. *eye roll* 
 Kees begins training Ella in her magic, which is what her dark power really is, and the history of Wardens, which Ella has the potential to be, and Guardians, partners of the Wardens; they begin tracking other Wardens and Guardians; there's some sex; a little action; and a fair amount of boredom. It took me almost a week to read it and that's never a good sign. The pacing was slow with not as much action as I anticipated. And the romance? Meh. I didn't feel the heat, ever, not even during the sex scenes. I even put down the book twice in the middle a sex scene. O_o 
 Warren does have a sense of humor and a knack for description, such as: 
 Deep and intense, his eyes shone with an inner fire that burned so clearly, Ella was tempted to reach for a skewer and a marshmallow. 
 I didn't love "Heart of Stone" obviously, but I didn't hate it. Ella, though spineless and whiny, could be funny and did develop some strength as the story went on. Kees I never warmed up to. The world building is good, again not great, but there's lot of potential with rebuilding the Order of the Wardens and the battle between good evil. I might, at some point in the future, try a second book.