I went into this book with very high hopes, but unfortunately, it just didn't deliver. 

The Leviathan had a really great concept. 
Toying with the idea of witchcraft accusations and a God-defying main character in the 1600's caught my attention. For the entirety of Part 1 I was really excited to see where it would be taken, I thought that the setup was interesting & the atmosphere was done really well. I found it really interesting the switch in time settings, so we were reading what was happening in 1643 alongside the story that was unfolding in 1703. While the bulk of the story took place in 1643, getting small hints and glimpses of the aftermath of those actions and the subsequent future was enough to keep me engaged. I truly believed that we'd be getting a more witchcraft focused plot, which we unfortunately did not. 

-- SPOILERS AHEAD, SPOILER FREE BLURB AT THE BOTTOM --

It started to fall apart a lot in Part 2.
This was where we were introduced to Esther's demon-self or possession arc. It was weird, I'll admit, but I did stick with it because it was interesting & I wanted to see where it would go. Was Esther the witch? Was Chrissa cursing her? What was going on? I was also asking questions related to the blurb - we had been promised a sea monster of some kind, where was that? None of these questions were ultimately answered. Thomas & Chrissa/Mary began to sort of work things out which was, in and of itself, kind of interesting, but I really didn't care. None of the characters gripped me. 
Part 2 was also where the writing really started to drag on & I found myself forcing through it hoping it'd get better. The atmosphere was still okay, but I wasn't scared by it so much as I was bored.

By the time we got to Part 3, I was just waiting for it to be over. I figured that this was where we'd wrap everything up & start exploring the consequences, the story, and actually get down to the root of what had happened and where we were going from here. But nope! With maybe 100 pages left, we introduce the concept that Esther is some demon foundling child that's probably not human, and we get introduced to the sea monster, which apparently attacked Thomas' father's ship once. It had literally no purpose to the story other than to insinuate that it was made from the devil & might have contributed to Esther being found in the cargo hold by Thomas' father. The whole twist of her not being human and bringing in this sea creature felt so cheap, especially when Thomas went back out into the ocean to save Henry after Esther kidnapped him. And I know that when I summarize it, it sounds super exciting, but it wasn't. It was so boring. I was hoping for something more, a bit more nuance, something to actually warrant how boring Parts 2 & 3 were. 
Even with the part that then takes place in 1703, how we finish up the book, I didn't care what happened or why they were doing it. Again: NONE OF IT MATTERED! It was so cheap, and clearly trying to make the reader feel scared or emotional, but the only thing I could think the entire time was "Why do I care?"

-- SPOILERS END --

Overall, the book was boring. I didn't particularly enjoy reading it, and apart from a pretty well done atmosphere, I think a lot of the book fell really flat. There were too many concepts here and it felt sloppy and rushed, giving the reader this feeling of being completely unsatisfied. Each part felt like a completely different book plot, and where it lacked that cohesiveness, it didn't make up for it in excitement or interest. 
Just a bit disappointing, because I was looking forward to this read.