All Lost Books in Harbiyah: In Assassins Creed Mirage

The Tale of Baghdad - Holy Mission Book: Head to the northern part of Harbiyah, near the Nestorian Monastery. You'll see a map icon for the 'Tale of Baghdad - Holy Mission' nearby. The Lost Book is actually underground, and you can spot its glow with Eagle Vision. The easiest way to get to it is via a Secret Entrance marked on your map, just south of the book's icon. It looks like a set of stairs leading down.

Once you're underground, you'll be in a basement area with some shelves. You need to pull these shelves towards you to clear a path. Start with the shelf furthest from where you entered, then move the other two closer together. Behind the last shelf you moved, you'll find a hole in the wall. Go through it to find a chest with some upgrade materials and an unbarred door. To the left of the chest, there's a cloth hanging like a curtain – go through that, and you'll find your first Lost Book!

Kalila wa-Dimna Book: This next one is in the southwestern part of Harbiyah, close to the border with Abbasiyah. Look for the Great Mosque; the book is a bit southwest of there. If you climb the Viewpoint north of the Great Mosque, it'll mark a Historical Site southwest of that, which is exactly where this Lost Book is. So, you'll be grabbing two things at once!

The building where the book is located has barred doors. To get in, go around to the south side and look for an open window. Climb through it and head towards the stairs. Through the bars, you should spot a red jar. Use your Throwing Knife to hit the jar and make it explode. This explosion will unbar the door right below the window you climbed through.

Climb back out the window, enter through the now-unbarred door, and you'll find the Lost Book sitting on a table. The 'Kalila and Dimna Historical Site' is also right there, so you've collected both!