How to start my book's opening sentence?

From my experience in trying to start something new, i find it usually best to go with inspiration, not what i think up as a starting line. Your style is unique to you as your fingerprints. Let yourself go to whatever sounds good and do editing later. Just write for a while. In this case it seems you have two opening lines. That is just my opinion. Either one states the books nature, and can be used independently. Maybe use the other phrase later in another chapter as an opener. Good luck, hope it helps, and i'll be looking for this on the shelves.