What are ways to curb the running away behavior. It always happens at the wrong time. We are in the Library, we set him down for two seconds and he is gone. Any advice?
Try a set of reins (suitable from when starting to walk 'til about 3 - when you stop depends on when they learn to stop running or wandering off!!)- not sure where you're from, but most shops like Mothercare etc sell them. I used them with my three children and it prevented then from making an escape bid. There are lots of places far more dangerous than a library where you want to prevent him from getting hurt or lost. Some people don't like them, as they think they restrict their child - duh!- that's exactly what they're meant to do, until they are a bit older and learn to stay close by. I see parents regularly running after little children who are close to roads, water or an escalator in a shop. I think I know which situation I prefer.....
Sounds like your son is enjoying himself and turning this into a game. How do you react once you have retrieved him? You must be quite firm and show him this is not a good idea. I agree with the advice already given, use reins or keep a strong hold of his hand. It is his safety at stake and you cannot afford to risk this, there should be no compromises with safety. Good luck