Players can find her journal in town in Acts I to III, a new part unlocking after each major main quest. Basically, every major plot event is recorded by Leah.
If she sees player picking up the book, she will comment on that, asking if it's polite to nose into her belongings.
Interestingly, she continues to record events even while busy with holding the Black Soulstone with her powers, despite having, to put it mildly, little time to write.
Collecting all entries is required for the respective achievements. Note that they can only be obtained in Campaign Mode, and only in (sometimes not so obvious) key plot points.
- "Uncle Deckard gave me this ring before our first exploration of the ruins in the Festering Woods. He said that it would protect me, and for a time, it did. I always intended to return it to him" (about Leah's Ring)
- "The dead rise again in the wake of the fallen star. Is it the mad king, Leoric, who birthed this curse, or does the humble village of Tristram somehow bring these ill omens on itself?" (about Leoric's Gauntlets)