It isn't normal but it's a common habit among puppies.
There are a couple of ways to discourage this disgusting behaviour. The first way is to "booby-trap" the feces by spraying it with a taste deterrent such as Bitter Apple spray. You must do this with all the stool and do it consistently for a couple of days.
The other method is to buy a powder such as Forbid from your veterinarian or pet supplier. You must mix the Forbid in the food and it imparts a horrible taste to the feces . . . although I can't imagine that feces taste good to begin with Usually you have to feed the Forbid at each meal for a couple of days.
Another method is to simply clean up the stool as soon as the puppy produces it. This obviously requires a little more diligence on your part and the puppy does not learn that eating stool is bad. Fortunately, they often grow out of this behaviour.