Assassin's Creed Revelations can frustrating, but is overall worth the time. Focus on making money, and farming the templar dens for apprentice's xp. The guides are getting better, if you get stuck. Relaying on R1 Square(s) with a few kicks will solve most combat situations, will your assassins can take down anything. You can fight off 20 or 30 elites with blocking and spamming Square. You can also work around the den defense with a level 15 assassin if need be.
All the games rolled into one excellent graphics, moves, character control , and a great story that just keeps getting better . The only downside is it is extremely glitchy, meaning solid objects like you or your weapons go through walls or other solid objects at times and the most annoying one I think is when you enter combat the comp. likes to move the camera into a tree or a wall, totally obscuring your view until you move it. Other than that definitely worth a rent!