If you had to limit yourself to just one book, this should be that book.For novices, this book has excellent basic advice for getting started, including many pictures and of how to display and plant them. For those with more experience, the book is a handy first reference before searching a specialized botanical tome.
This book makes the specific point that (popular, commonly available) cacti are no more difficult to grow than any other house plant.
The book thoroughly covers the needs of these plants, including what kind of soil, how much water, what temperature and amount of light they prefer.
The largest section has all of the popular genera, including the tropical varieties. This section has excellent photography of the plants at their best. If a person had a cactus that's in this book, that person would very likely be able to identify it from the descriptions and pictures. The book usually describes the distinguishing feature that classifies the plants of that type.
Typical and maximum sizes are given, along with the plants' growth habits and the age at which they first flower (some varieties do not flower until they are many years old).
Also included in this section is the hardiness, or how cold the plants can get before they die. If you don't live where these plants naturally grow, this is very important information. For instance, many kinds of cactus grow where it snows in the winter and can be grown outdoors in most of the USA.
At least one of each of the different general forms of cactus is shown: columnar cacti, prickly-pear types, barrel types, etc.
Following the section on specific cacti is a fairly representative section on popular succulents. There are so very many different kinds of succulents in the world, even a book ten times thicker would barely scratch the surface. This book concentrates on those species which are most commonly planted alongside cactus.
The lists at the back of the book are almost worth the price of the book itself. There are lists that categorize cacti and succulents in every which way, including many species that were not pictured or discussed in the main sections. There are lists by how easy the plants are to grow ("easy", "moderate", "difficult"), lists by temperature range ("cool", "temperate", "hot"), and other useful groupings. These lists help make this book continually valuable, even as one's experience and knowledge grows beyond the basics.
This author (Terry Hewitt) has written other books on cacti and succulents. Those books are also excellent, and worth purchasing for the unique information that they contain, but mainly as supplements to this book.
There are also other excellent cactus books that are more complete, but also more technical - or more specialized (for instance, there is an entire reference work on just the "opuntia" (prickly-pear) species).
This book is perfectly written for the average amateur cactus lover.