For the most part you're right Zieveraar, but there are a couple things to expand upon.
1st You don't always take them to Gandalf, you take the books to various NPCs. Hunter I bet go to Legolas, I know champions go to Gimli, and Lore Master to Gandalf. The last two I know for sure, and i'm just guessing on the Hunter considering they seem to be using fellowship members and Legolas was the Hunter of the fellowship.
2ndly Pages and books are VERY hard to find, they all have a low drop rate, under 1% easily. For example, I had to kill 300 mobs to find 4 pages (I got lucky and literally the first kill I made of the mobs after I activated the book dropped 2 pages), but i've heard of people killing 500+ of the same mob for their 4 pages... and then you have to repeat on a different mob type.
Finally, each class gets 3 books, maybe 4 i'm not too sure on the exact number. All drop from Humanoid (ie two legs, arms, stands upright all the time) mobs and can be traded/sold. Each of the books have a different drop source for pages for it, these don't always obey the humanoid rule. 1 book's pages will drop all the time, whether you have the quest or not, and only drop from humanoids 39 or higher. Those pages can be traded around like the books. The other books you have to farm for the pages yourself.