I have to say I was hooked from the beginning. That isn't usual for me. I found I didn't put the book down nearly as often as I should have.
I agree that it was strange that there were no cell phones. When I stopped considering the book as futuristic and considered it (well, blast, can't think of the proper word! LOL) a different development of society, it was fine. When I thought of it as a different Earth, I had no problem with the lack of cell phones.
I found the parts in the past more riveting than the present but enjoyed the whole book a great deal.