Yes, the action really ocurred. It sounds like something that Hollywood should have made a movie about
This account is in several other naval books. It's a classic "David and Goliath" and stands as a tribute to the US Merchant Marine and the Naval Armed Guard personnel. The Hopkins was simply in the wrong place at the wrong time, but a Liberty ship can't run from much of anything let alone a German raider, so the crew bravely opted to fight. The action might not get more notice because that it was a "secondary" area versus one of the big battle fronts and also the ship wasn't "Navy" it was Merchant Marine - the USN has a better PR machine.
This action, and a few others is why I chuckle inwardly when the arship fans start going on about the capabilities of one ship over another. The Hopkins/Steier action shows that fortune and bravery can match technical superiority.