Fable III: Traitor's Keep Diaries
Similar to the Rare Books you may have come across during Fable III's main storyline, in Traitor's Keep, you'll find a collection of diaries scattered about the new locations of Ravenscar Keep, Clockwork Island and the Godwin Estate. Each location has five diaries specific to that location's main criminal, so all of General Turner's diaries can be found around Ravenscar Keep, for instance.

There's no particular in-game award for collecting all the diaries, but they will give you some more insight into the backstory. Additionally, there's three achievements for finding them all, called A Revolutionary Idea, Diary of a Sad Man and Lab Notes. Below, you'll find the locations of every last one of the diaries. Note that you'll need to return to some of the areas after you've finished Traitor's Keep's story to find all of them.

General Turner's Diary Entry I General Turner's Diary 1/5 (Ravenscar Keep Interior)

Entry I: You'll find this diary on the upper floor of the Keep. Climb your way up the stairs via the cell blocks, and make your way to the central room. You'll find the diary on one of the tables.
General Turner's Diary Entry II General Turner's Diary 2/5 (Ravenscar Keep Interior)

Entry II: Search the kitchen to find this diary entry on the table. The kitchen can be found by taking a right immediately upon entering the building from the front door.
General Turner's Diary Entry III General Turner's Diary 3/5 (Ravenscar Keep Interior)

Entry III: Once you've started the quest Heroes and Villains, you'll find this diary entry in plain sight sitting on a crate as you follow the hidden passage down from the records room.
General Turner's Diary Entry IV General Turner's Diary 4/5 (Ravenscar Keep)

Entry IV: You'll find this diary near the gallows. From the Keep's front entrance, turn around and follow the path running opposite from it.
General Turner's Diary Entry V General Turner's Diary 5/5 (Ravenscar Keep)

Entry V: From the docks, head towards the stairs leading up, but turn left at their foot, open the gate, and you'll find this diary a short distance away.
Professor Faraday's Diary Entry I Professor Faraday's Diary 1/5 (Clockwork Island)

Entry I: You'll find this first diary entry on a crate after vaulting down from the Street of the Future into the canal below.
Professor Faraday's Diary Entry II Professor Faraday's Diary 2/5 (Clockwork Island)

Entry II: Make your way along the canal to where it ends in a collapsed sewer tunnel. Turn left and head inside the factory, then check behind the wall in the corner; the book is lying on the ground.
Professor Faraday's Diary Entry III Professor Faraday's Diary 3/5 (Clockwork Island)

Entry III: After you've climbed up the stairs to the rooftops, you'll find this diary sitting on a crate next to a crane and one of the generators you turn off during Reconstruction.
Professor Faraday's Diary Entry IV Professor Faraday's Diary 4/5 (Clockwork Island)

Entry IV: Right before facing off with Faraday, you'll find the fourth journal entry on a crate as you climb the catwalk.
Professor Faraday's Diary Entry 5 Professor Faraday's Diary 5/5 (Clockwork Island)

Entry V: You'll need to turn off all three generators around Clockwork Island to reach this last diary entry, which is hidden behind the electrified gate you need to disable during Reconstruction.
Mary Godwin's Diary Entry I Mary Godwin's Diary 1/5 (Godwin Estate)

Entry I: Mary's first diary entry is sitting on a bench as you enter the garden area, right next to the Topiary Swan exhibit.
Mary Godwin's Diary Entry II Mary Godwin's Diary 2/5 (Godwin Estate)

Entry II: From the electrified gate, turn left and head back towards the cemetary. The diary entry is sitting on a hedge next to the combustible monkeys' pen.
Mary Godwin's Diary Entry III Mary Godwin's Diary 3/5 (Godwin Estate)

Entry III: During your visit with Milton, you'll disable a generator to shut off the electrified gates. The third diary entry can be found behind a stack of crates near the generator building, through the cemetary and across the stone bridge.
Mary Godwin's Diary Entry IV Mary Godwin's Diary 4/5 (Godwin Estate Basement)

Entry IV: As you make your way through the basement of the mansion, you'll come across a room with a dirt floor and some miscellaneous lab materials scattered about. As Milton stops you and points out this diary entry during The Menagerie, it's very hard to miss this one.
Mary Godwin's Diary Entry V Mary Godwin's Diary 5/5 (Godwin Estate Basement)

Entry V: This final diary entry of Mary's can be found upon first entering her lab, resting in plain view on top of a generator.