Spanking, bold, head-on images--that put other sign-displays in the shade. Once again, Hoban assumes that, for kids, things are interesting in themselves: in this case, street signs and the international language of symbols. Street signs are for reading here: WALK on one page, DON'T WALK opposite. (You can't see them both at the same time on the street.) BEWARE OF DOG, cagily, behind a chain-link fence; NO PARKING, FIRE LANE, smartly, on a row of stanchions; RAILROAD CROSSING paired with TAXI, NO LEFT TURN with (of course) KEEP RIGHT. Also, yes: COME IN, WE'RE OPEN to start with--and SORRY, WE'RE CLOSED at the close. Big as the signs are, in their color-photo-rectangles, it's a lot like looking at the TV screen--another dimension that will do no harm. The symbol book, by nature, is something of a conundrum--challenging youngsters to guess what the wiggly arrow or the big white H means, teaching them the symbols for ladies' room and men's room, acquainting them with the very idea of a symbol language. (At the close is a pictorial key to "What the Symbols Say.") Both are simple, instructive, and dazzling.