As a reviewer said on the book jacket, this book has a Narnia feel to it and I concur. There is a lot of mythology, but Wright attempts to provide a scientific basis for the gods. I found a lot of good discussion on morality and was definitely mentally engaged. The book is a little weird for sure, but highly entertaining.
The middle is a little slow, but it finishes with a bang. The characters are well fleshed out and believable.
I definitely recommend this book and I look forward to reading the second.