Leah's Caldeum Journal is a tome found in Act II of Diablo III, second part of Leah's Journal. All parts of it can be found in the Hidden Camp near where the Followers gather during different points of the act.
The parts read as follows:
Quest: Shadows in the Desert
Caldeum — everything Uncle Deckard left me leads to this place. It's strange; I first met him here when I was only a child... and now his loss feels heavier than ever. He was right about everything all along... We have to stop Belial before it's too late.
Quest: The Road to Alcarnus
The city has many secrets, and I still remember most of them. I can get into Caldeum through the sewers if I avoid the Imperial Guard. While I'm out, my friend has sworn to take down Maghda. It won't bring Uncle Deckard back, but we'll all be relieved when she's gone.
Quest: Unexpected Allies
After all this time, my mother is alive! I couldn't be happier, and yet it's still hard to accept that she never sent word to me or Uncle Deckard. She said that she wanted to keep me safe, but I just wish I'd known... Well, at least I have her now.
Quest: Blood and Sand
My mother has been teaching me magic and how to control my power, but I feel like I'm constantly disappointing her. She says that I have a gift, but it doesn't feel that way. Maybe it will improve if I keep practicing. For now, we are getting closer to the Black Soulstone, and that's what really matters.
Quest: The Scouring of Caldeum
We have the Black Soulstone at last, despite Zoltun Kulle's betrayal. I always knew he couldn't be trusted. Fortunately, we were able to defeat him and retrieve the stone. I learned that my mother had secretly bound the fallen Lords of Hell to it... I just wonder why she didn't tell me.