You should give them a try sometime Azzizi. Supermarket ones can be OK (and will be safe as you know you are not getting toadstools) but, if the US is anything like the UK, avoid the little button mushrooms as they are so tasteless.

A simple one to try: Get one of the larger ones, peel it, sprinkle a tiny bit of salt on top and grill for a couple of minutes. Eat it on a peiece of buttered toast.