My brother and I always enjoyed the series of 'I Spy' books available here in Britain on such topics as Cars, Registration Numbers, and unusual vehicles. These were ideal for long car journeys, and points were awarded for different cars, for instance, a very common Ford Cortina might score 10 points, while a Lotus Elite might score 50. Registration numbers showed which city a car was originally registered in, for example EGG 346T would come from Glasgow, as would all plates beginning in _GG, or indeed _GA, _GB, etc. The books were liberally sprinkled with photographs of cars of the different types or showing the different registrations.
The idea was to spot the car or registration number before your sibling, and dash to grab your book and scribble down the number, or tick the box for your car or other vehicle. At the back of each book was a certificate which could be sent away once you'd reached 15,000 points or so. The books were available in most bookshops or newsagents. I'm sure my parents were glad to have us so innocently amused. Great fun!