Excited, nervous, or filled with suspense while one waits to find out what happens next. Often said of those viewing a movie or TV show. The image is that of one literally sitting on the front of their chair because they are unable to sit back and relax. More commonly seen as "on the edge of (one's) seat." It's not going to win any awards, but the film certainly kept us on the edge of our chair from start to finish. I've been on the edge of my chair waiting for my acceptance letter.