Do experience gain bonuses from items and the Adventurer ability stack in Torchlight? Do experience gain bonus items worn on my pet add to my experience gain as well?
Experience gain from items on a pet do not stack or affect your character in any way.
Bonuses from items and the adventurer skill stack in this way:
If you have +10% from the adventurer skill, +2% from a ring, and +5% from a necklace, your experience gain will be 10+2+5=17%.