Diablo Wiki
For the in-game zones, see Northern Highlands and Southern Highlands.

The Highlands is a tome in the Act I of Diablo III. It is found inside a Lost Chest somewhere in the Southern Highlands, usually near a tree or similar object, no need to be on any particular quest for the chest to appear.

It reads as follows:

"Though New Tristram and the fields surrounding it have been resetted over the years, the Highlands remain empty save for the crumbling ruins of Leoric's old outposts. The king built more than one watchtower in his paranoia but now they cannot even ward away goatmen and wild beasts. A tragedy, really.
Abd al-Hazir