If you live in the desert, you MUST purchase Mary's books. They are an invaluable resource. I own everything ever published. In fact I ordered two (Arizona Gardener's Guide & Gardening in the Desert) before I even moved to Arizona from England. They were here waiting for me so I could get to the task of gardening in a new climate right away.
This particular book of perennials is wonderful. It supports Mary's previous works by giving useful information on the varieties of plants that do well in our desert climate. This allows the desert gardener to move beyond cacti, agave and spoon grass and try for a bit of colour.
If you live in the desert, buy this book. Buy all of her books. They will become worn quickly as you reference them again and again.