There are tons of things you can do in Grand Theft Auto V: The Manual. For example, you can use your jet ski to fly through bodies of water and hang around in towns and airports. You can also go on bike tours and go on a wild goose chase through the countryside. You can use your boat to sink other boats and steal their contents for parts. If you're feeling adventurous, you can even try and hijack an airplane and try to deliver it to a specific location. There are also plenty of military missions you can try, including commando missions to take down terrorists or capture targets from the sky.
It's not surprising that this game is very addictive. Even if you've played the game before, you'll probably find that this is much more difficult than the previous versions. It's because the game was rebuilt from the ground up and features a more open environment. In fact, the graphics have been completely redesigned, so even the slightest detail of the scenery is incredibly crisp and clear.