I loved the Bourne movies. In looking for a quick read, I picked up The Bourne Legacy by Erin Van Lustbader. It was a quick read and the opening chapter in Chechnya was really well written. However, there was quite a disconnect from who Bourne was in this book and the three movies. I never quite got used to it.
I don't know if the three books the movies were based on were quite as different as this book was from the character in the movies, if so then I'm comparing apples to oranges. But if not, There were a couple of story developments that put me off. First, Bourne was always getting his butt kicked. He never lost a fight in the movies. Second, I was surprised that there was such an emphasis in the last two movies of him not killing people whereas it wasn't even mentioned in this book. I also didn't buy Bourne and Khan's history. It seemed to come out of the blue (again based on the movies). Their flashbacks really put me off.
If you've only seen the Bourne movies, I would not recommend this novel.