Two kinds of reading are helpful for visitors to Pompeii.  Rick Steve's Italy 2006 has useful information for trip planning, with good suggestions about reasonably priced and atmospheric hotels, restaurants, and detailed information about getting around on public transportation.  His directions for the Museo Nazionale in Naples (where many of the artifacts from the Pompeii excavation are housed, were clear and easy to follow).   

If you have even a casual interest in historical background then several books provide accessible introductions.  For both adult and child visitors, Peter Connolly's Pompeii provides beautiful illustrations that reconstruct the housing, art, and technology of the ancient city. My favorite introduction to the history of the city is Salvatore Nappo's Pompeii: A guide to the ancient city which is only available from Barnes and Noble. It may be out of print at present, but the used book search engine has some very reasonably priced used copies. The authoritative and readable text is paired with beautiful color photographs, maps, and floor plans.  I would also recommend Amery & Curran's The Lost World of Pompeii.

You can buy a reasonable guide book and map of the Pompeii excavation from one of the numerous vendors outside the entrances; this is a must, because it isn't easy to find your way around without at least a schematic map. The "guides" who provide narrated tours can get you to the "hot spots" such as the Lupanaria brothel with the minimum of wandering about lost, but they are fountains of misinformation. If you want an accurate description of first century life, you need a book, not one of the local guides!

If you want a "you are there", intimate account of life in Pompeii, the Robert Harris Pompeii suspense novel is a good choice; it describes the last days of Pompeii from an unusual point of view, that of the engineeer who is responsible for the failing acqueducts.   Bulwer-Lytton's "The Last Days of Pompeii" has probably sold more copies than any other novel set in Pompeii.  Bulwer Lytton did have some knowledge of archaeology, but modern archaeologists understand a lot more than the archaeologists of his time, and his book is full of misconceptions (such as people driving around the city streets using chariots for everyday transportation).  His novel is more informative about the sensibilities of Victorian England than about the nature of daily life in Pompeii. My personal favorite is A. D. 62: Pompeii by Rebecca East; in this historical fantasy, a modern woman experiences life as a slave in a wealthy household in Pompeii. Through her eyes, readers get a reasonably accurate idea of how people lived in the wealthier parts of town. 

Pompei,The Day a City Died by Robert Etienne is an excellent account of the excavations of this great city.It gives the whole history of the site from when first discovered till present day.It tells who was involved and in what time scale.There are numerous drawings maps and photographs of the various stages of excavations as well as images of what things may have originally looked like.there is also a section with letters from famous people on the Grand Tour describing their visits to Pompeii.All in all and excellent insight into one of the Wonders of the World.

For a comprehensive photographic record of the remains as they are today, including the areas closed to the public and to help plan your trip or identify your photos when you get back, take a look at  .

Pompeii is a very intresting city to learn about!