To sort of answer my own question from earlier, it seems that:
You can repeat the missions an unlimited number of times and get one authorized book each time, customized for the character who did the mission. So you can get an unlimited number of items if you like.
You can also earn 3 "account-wide" books by doing the bonus objectives for the first time with any character. Any character claim these books, even if they weren't the one that did the mission. You only get 3 of these per mission ever.
So, it seems that you can get as many items as you want
Meh I'm kinda glad they aren't tradeable, that would make me go earn money again, and earning money is boring.
* goes back to PvP and ignores nice skins *
To sort of answer my own question from earlier, it seems that:
You can repeat the missions an unlimited number of times and get one authorized book each time, customized for the character who did the mission. So you can get an unlimited number of items if you like.
You can also earn 3 "account-wide" books by doing the bonus objectives for the first time with any character. Any character claim these books, even if they weren't the one that did the mission. You only get 3 of these per mission ever.
So, it seems that you can get as many items as you want
Thanks, thats good to hear. Time to turn in my books .