The Traveler's Journal is an item in Momodora I.
Probably the last item you acquire in Momodora I, it works like all the collectables: It gives no benefit other than the warm feeling of completing the collection.
It can be found at the save point room that leads to Area 8. Just go down to the exit in the floor, but instead of dropping down, go to the left and destroy the blocks there. The Traveler's Journal is hidden behind the stones.