Primary Sources
Bloodstained Letter - The Keep (Needs confirmation)
Ghom's Log - The Larder
Journal of Hansan Haile, Captain - Bastion's Keep Stronghold, near Vidar
Leah's Journal (13-16) - The Armory, below Leah
Morgan's Journal (1-3) - Morgan's Satchel, Skycrown Battlements/Stonefort
Espionage
Battlefield Reports - Battlefields (walk backwards from Bridge of Korsikk, fallen soldier has blue exclamation point above head)
Orders from Azmodan (1-6) - Messenger of Azmodan (Skycrown Battlements, Stonefort, The Keep, The Battlefields, Fields of Slaughter, Arreat Crater)
Historian of Arreat
Fall of the Barbarians (1-5) - Misplaced Packs, The Keep
The History of Bastion's Keep - Librarian's Scrolls, The Keep
For the beast lore, I believe it is fairly straightforward to obtain by killing all the new monsters in Act 3, but I will look for a good source. It is difficult to describe their locations since many are randomly generated.
Best Answer
It's actually in the Act IV hub (Bastion's keep stronghold), north of the waypoint [at least during quest 1]. It's on the corpse of Martha.
You can go there by using the portal (Click on T) It is rather easy to miss actually.
Screenshot