Title.

You didn't really give any details- HOW are you getting two? Is an NPC giving them to you? That would probably be a bug. But if you're in a bandit cave or dungeon and happen to find two notes, that's on purpose- it's in case you didn't see the first one.

Also, the same books are everywhere in the game, for the same reason. The game doesn't know which direction, which town, which dungeons you're gonna go to first. And what if you skipped over books the first half of the game, and suddenly decide to start reading them? It would svck if all the books were unique and you had to go back to every place you'd ever been just to find them again.

Also, as far as notes go, in time you may find you have more than one copy of any note that is generated by Radiant AI. The notes found on Dark Brotherhood assassins sent to kill you, for instance.

That happened to me, but only on the Expedition quest - each journal I retrieved put two copies into my inventory, even though there was only one copy to loot. Haven't encountered it anywhere else so far, though.

Ahhh, thats what it is.. ive gained 2 from each Expedition quest journal.. thanks for helping me figure that one out xD