Throughout the book, the writer replaced the number "1" with an "I", but only on the chapter and page number. Why is this? At first I thought it...

Well, I have to say, I never paid too much attention about the "o"s and "I"s. I actually thought that it's the typeface's style. Anyway, I can try to explain the "I"s like this: "1" in the book, refers to God, or gods, and religion. The three different religions mentioned worship different gods but they all come down to one center belief of love in god and the world. Religion is in itself also a kind of way for men to relate themselves with the world. So, hence from changing "1" to "I", is the gesture of relating religion to oneself.

But on second thoughts, what I just did is probably an overanalysis (XDDD) so you can just delete it from your memory.