The book is different physically from the others since it consists of sections of text with largish drawings.
The background of the village is given. Caesar tells them that if they perform twelve tasks then he will surrender to them. He provides a guy to oversee the tasks and their results.
The tasks are:
1. A footrace with Asbestos, a Greek, which Asterix wins.
2. A javelin throw with a Persian. The guy's javelin lands in a Native American village. Obelix throws and his javelin goes all around the world.
3. A German wrestler who beats Obelix but loses to Asterix.
4. The Isle of Pleasure where they must resist the women there.
5. Look into the eyes of an Egyptian hypnotist.
6. Eat everything fixed by the chef of the Titans.
7. The Cave of the Beast.
8. A place that causes people to go mad (a government bureaucratic place, naturally).
9. Fording a river filled with crocodiles.
10. Climb a high mountain and answer a riddle from a guy there.
11. Show they are not scared by ghosts.
12. Survive the Circus Maximus.
All the tasks are completed, Caesar retires, etc. Quite funny.