Tomes are the brown symbols on that map. There are 64 of them. However, some might be commentaries for Gat or Kinzie. Anyway, before starting this make sure that you are respect level 15. Then go to the upgrade store and go to "abilities". from here, purchase "Collectible finder". Now they all will appear on the map. No need for a collectible map online. To make it easier, go to the map and make it so it will show collectibles only.