Pompeii is definitely a must-see! When I was there, they sold a little book called "Pompeii-Herculaneum Past and Present". It has descriptions and pictures of the ruins, with plastic overlays for many of them. The overlay shows how archaeologists believe the site originally looked. It helps to visualize the original look.

There is also a Past and Present book for Rome. It's even more helpful since many of Rome's ruins are more ruined than Pompeii.

Marguerite in Chicagoland