Zero Sum

I have to be honest, I was a bit disappointed in Zero Sum. I've read Livia Lone by Barry Eisler and really liked it. Maybe it was due to the fact that I didn't start with book #1 of John Rain? I picked this one up in a used book store. The story was a bit slow at times and filled with (in my opinion) unnecessary dialogue. Sexy times in the book were a plus, but I felt all the characters lacked in back story and needed to be more fleshed out.