Here, have another:
The opening of the first sentence just sounds awkward, which is why I changed it.
Um… previous past lives? As opposed to what, current past lives or future past lives? *shakes head* Delete previous.
At birth, each person is given a book containing the memories of their past lives. Today your book was inexplicably stolen.
Well, if the theft was inexplicable, you know the rest of the story won’t be about why or by whom the book was stolen, right? That’s too bad, because it would have made a decent supernatural-ish mystery…