Very interesting! I enjoyed the first two time periods so much that I didn't want it to end. 
The last time period which is in the future was very hard to follow at first, but I want to believe it's because I do not know any Spanish so I had no idea of the Spanish words and conversations. But I later found out there's a glossary in the back so I was referencing it while I read which was very helpful!
As I said, the first two was amazing, I especially enjoyed Leah's story. The Mayan time period was interesting too but during the middle part I felt the plot dragged out a little bit but eventually picked up and things got INTENSE. 
I love the ending which is basically all of Book 3 it was just so fun to see everything finally align together.
It wasn't an absolute five-star read but close enough! Definitely recommend!