From Diablo Wiki
The Traveler's Journal can be found on an adventurer's corpse along the Old Tristram Road. You do not need to be on any particular quest for the corpse to appear but you will most likely be on the very first quest, The Fallen Star.
Only one of your characters needs to find the journal for you to be credited with it.
To find out which journals you have found so far go to your Achievements list (press Y) and check:
- Campaign > Act I > Historian of Tristram
|Adventurer's Corpse lore loot|
|Found on an adventurer's corpse along the Old Tristram Road in Act I.|
|Part||Text||Found on Quest|
|1||While exploring a cave with hopes of finding hidden treasure, I came upon a most grisly sight - a heap of dead bodies. Unbelievably, as I was searching them for any items of value, they began to rise! I must tell them of this in New Tristram before it's too late. -- Theren the Traveler||The Fallen Star|
Traveler's Journal is in some way involved in the following achievement(s).
| Books & Lore of the
|Tomes - Lore Books  In-game: People World/Quests Bestiary Diablo I & II Extra: Manuals/Other Novels History|
|Diablo I Tomes||Diablo II Tomes|
|Diablo I Manual||Diablo II Manual||D2: LoD Manual||Diablo III Manual||Other sources|
Abd al-Hazir (Writings)
|Diablo novels||The Sin War Trilogy||Diablo III novels||Diablo comics||Other books|