Without fully understanding the environment it is honestly difficult to say. If you are expected to be at your desk coding that entire time I would say it is completely unreasonable and would run for the hills immediately. However, if those people you say are working 10-13 hours a day, but in reality they are talking, playing ping-pong, out to lunch, etc.. during that time it really isn't 10-13 hours. That's just poor time management. It could also be that management doesn't do a good job of keeping projects in check so that leads to longer hours worked to finish projects on time. Going back to the reading question though, some people may view sitting at your desk reading as not working, while at the same time they will play ping-pong for the same amount of time. There can be a perception that if you are interacting with others you are "working".

I am probably the wrong person to answer this question though. I am not a firm believer in structured work hours unless there is an absolute customer requirement. I have hours in the day where I am more productive and hours where I am completely unproductive. I have learned to manage that to maximize my productivity. However, during those "down" hours some may view it as not being productive, but what they don't know is that I have been up since 4am and probably got more done by 7am than they will all day. I view it as if the job gets done properly and on time it doesn't matter how it gets done.