A shopper ambled up to the counter and asked, "Do you think I'd like this game?" At almost any other shop, the answer would be that the salesperson didn't know anything about the game. At Wonderful World of Games, though, the answer was, "You'll like it if you like to kill people to win. I don't." This is a game shop unlike any other. First, it is about as big as a modest-size living room, which it once was. More important, as owner Robert Williams put it, "We tell you what's inside the box." Mr. and Mrs. Williams stock hundreds of games, which they sell there and by mail order, through a free catalog. "The Game Board," which they publish every two months. They have played all the games they sell. And they will teach you to play - or to play better - any game (theirs or yours) if you make an appointment for a free Saturday session. Once you're a player, they will help you finds others to play with; the shop has a bulletin board listing players, theier level of expertise, and when they are available. Wonderful World of Games. 314 Marshall Ave., Laurel. Open Monday through Saturday, 10 a.m. to 6 p.m. Free game lessons Saturdays, reservations required. 498-9346.