Sentence #1 is the correct one, although many people would not say it that way in common usage. Like Tony said, sentence #2 is the way most people would say it in spoken English, if you remove the word "them".

These are sentence fragments. This means something must be added to make it a complete idea. Depending on what you add will change the meaning - so I am left guessing what you mean. But here I go: I read this information in a chapter, which is one of the parts in which a book is divided.

1) one of the parts INTO which a book is divided. 2) one of the parts which a book is divided INTO.

Sentence 1 is grammatically correct. Sentence 2 could be, if you removed the "them" but it still sounds weird. It would sound better if you took "which" out. For example: One of the parts a book is divided into.

None of it correct. I can’t get your thoughts.