With the help of some guildmates and a bit of trial and error, here are some things that are confirmed.
I've been hearing a lot of different information going around, so hopefully this will help people on their Kat/Page/Book hunting:
-The books drop rarely in addition to pages you will get from random Black Kat spawns (except for ones in the prestige mission that drop nothing.)
-When the book drops, everyone who is present when it drops, will be able to pick it up. (Same as SL and Seerus mats.)
This means that anyone who joins after it drops ,but before drops are picked up, will get pages (since they are tokens,) but no book (since it is an item drop.) The book comes unbound, like any mat.
-When you take the book to Moorcroft and activate the dark ritual, beating the boss awards everyone 6 Pages (Confirmed by guild mates, not personally.)
In addition to this, the person who activated the ritual with the book, gets the hat (unbound) that comes with that.
This means: If you find a kat with four people in your party, and it drops a book:
1) Everyone will get a book.
2) Everyone will get a hat, if you beat the boss.
3) You will be able to do the Moorcroft "boss fight" four times, with up to 16 different knights (for 6 tokens each.)
Hopefully this helps people clear up some misconceptions.
[People, don't go begging your friends for invites to fight the boss, thinking that their book will get you a hat. That's not how it works, you need your own book, to get the special hat.]
Good information. Thanks for posting.