Do you need to keep a storybook in your inventory for it to update itself?
Ras the Swift Death
Or can I just leave it in my storage and it will update as I'm doing missions?
Iuris
It will only update if you have it on you when you do the mission.
If you don't have it with you, you can talk to the NPC that gives them out, and he'll fill the entries you've done in the last month, but for 100 gold per page.
If you don't have it with you, you can talk to the NPC that gives them out, and he'll fill the entries you've done in the last month, but for 100 gold per page.
Darcy
If you have more than one copy of a storybook, then only the first one in line will update. So if you are repeating quests/missions to fill books, remember to rearrange the books each time.