The Mephisto Covenant has a very interesting concept, and it's one that I felt I would really like since I truly enjoy stories that incorporate mythologies and religions. However as I began the book I realized this was a tad bit more religious than I normally enjoy reading, thankfully over the course of the book it scaled back on the 'preaching' and I didn't feel as irritated. I don't count this toward my rating at all because I'm a bit bias when it comes to religious aspects and it's not fair to the author. I did however have serious issues with the way this story flowed, as well as character interactions.I'll start with the flow. The writing is wonderful and the story had a great amount of potential, and I feel that a lot of people will enjoy this because it's somewhat original. I found the plot to be dodgy, one minute you are getting use to something and then scene changes or the characters personality suddenly seems to be different. I understand the character development where Sasha is concerned over the entire course of the book, but a few times in the beginning she comes off as 'trying to hard'. Jax is your typical bad boy who falls in love with the 'normal' good girl, he has a twist but it's essentially the same. It many ways it felt like Twilight to me since it read in the same mindless way, it's a quick and easy read but it won't leave any sort of positive lasting impression on me. Despite the easy flow of this I found it very hard to read and concentrate on, and I had quite a few moments where I simply wanted to quit reading it and review the bit I had managed to read.Now for the characters. I personally didn't feel anything for any of the characters, except annoyance. Eryx didn't bother me at all, which I feel is an essential trait for a bad guy. Jax and Sasha's relationship was annoying and flip-flopped more then fish out of water. Melanie's character just came off as another aspect that seemed "over worked", she was horrible like she was suppose to be but it was so over the top that it became childish and dramatic. There are times in the story where half of a conversation seem utterly pointless. I understand the need for normal conversations but there is a point where it crosses the line to 'filler' and becomes tedious, and this book has that problem at times. Also the word 'spit' is never an attractive way to describe a kiss and despite the fact that I know spit is involved I was repulsed at the mental image. The intimate scene I found to be too detailed for a young adult novel, and on the side of tasteless.Overall I obviously didn't enjoy this book, and I can't say I'd recommend it in an everyday book talk. I think those who enjoyed Twilight would like this, however only to those who over 16 because of the adult content. I received this from Egmont USA and Netgalley in exchange for an honest review.