Written by Ruth Rogers Clausen and Thomas Christopher, Essential Perennials: The Complete Reference to 2700 Perennials for the Home Garden (Timber Press, 2015) is a long-awaited update to a classic book.
An A to Z guide, the book contains entries on 2700+ plants, and although there are not photos of every single one, you can easily look up images online of the ones you don't know. What I particularly like about it is the essay at the beginning of each genus entry that tells you, for instance, whether the plant is susceptible to disease or insects, whether it might be invasive, how it's best used, and how best to plant and maintain it.
If the plant nomenclature has changed (such a maddening factor for designers and avid gardeners that occurs all too often), you'll find it here. The authors include the current botanical name as well as past ones. At the end of each entry, they list notable cultivars and hybrids, although obviously they cannot list everything, like hundreds of daylilys or hellebores.
At the beginning of the book, there's a section on perennial basics -- planting, selection, irrigation and the like -- and in the back of the book, there's a list of mail-order nurseries and an index of common names. You will not be disappointed in this book.
If you live in the Northeast, you might want to pick up a copy of Growing the Northeast Garden (Timber Press, 2015) by garden writer Andrew Keys. You'll find out the best plants for the region year-round, and which ones you want for a show in early to midsummer, late summer to fall, and winter. Toward the back of the book, there are case studies of seven gorgeous northeast gardens that will give you inspiration to get going on that garden plan.
And finally, a new book on plant basics, How Plants Work: The Science Behind the Amazing Things Plants Do (Science for Gardeners) (Timber Press, 2015) by horticulturist Linda Chalker-Scott. Loads of tips on planting, watering, fertilizers, weeds, what causes plant problems and much more. Yes, it will help you change the way you garden.