Disclosure: I received complimentary products to facilitate this post. All opinions are my own.
A few weeks ago, I reviewed The Goddess Denied by Deborah Davitt. I mentioned in the review that it was a good book, even without having read book two; after posting, the author contacted me and sent me an e-book of book one to fill in the holes.
I have to say I like The Valkyrie, book one of the Edda Earth series, even more than book two - however, I think I'll like book two after rereading it now that I've got more depth from book one. It's a great premise - Rome never fell, and the mythical gods coexist with science - that is very intriguing for anyone interested in mythology (which I used to love), fantasy (which I still love), and/or scientific pursuits (which I also enjoy). You can learn more about the Edda Earth universe here, and then download the e-books to read them.