Urag gro-Shub at the College of Winterhold is looking for four books written in the old-school Flamer Language. As all four books can be found in the Forgotten Vale area of the game, you’re best picking them up as you’re completing the main DLC quetsline 'Touching the Sky' (as you have to go through this area for this quest).
Urag will translate each book and pay you 1,000 gold coins as well (hence why it’s nor really worth going out of your way for them otherwise). The location of each book can be found below.
Unknown Book, Vol. I
From the Wayshrine of Learning , follow northwest along the river until arriving at the pillars across from the frozen waterfalls. There should be a chest, a skeleton, and Unknown Book, Vol. I next to the tallest pillar.
Unknown Book, Vol. II
Much more complicated to reach than volume 1 as you need to kill a certain hard-hitting Frost Giant who will have an Emerald Paragon on it. You need to take this emerald to Paragon Platform and use it here to unlock the way to Forgotten Vale Overlook
Once you’re here, head downriver - stopping and turning right just before the lower waterfall - to find a treasure chest with gold, potions and gems, some elven/dwarven weapons, a skeleton, and Unknown Book, Vol. II .
Unknown Book, Vol. III
At the Wayshrine of Resolution head west to cross the bridge. Now; traverse through the ravine using the Falmer walkways and the book is in the southern most tent near the waterfall.
Unknown Book, Vol. IV
After traversing through the Glacial Crevice, you will reach a small outdoor Falmer village. The book is located on a table in the top Falmer’s hut near the end village right before the long tunnel.