For the New Orleans area I would recommend Charlotte Seidenberg's "The New Orleans Garden". It has lots of description of plants that grow here as well as historical data and personal experience with the plants. Also, gives locations where one can view certain plants, trees, shrubs, vines etc.
For persons interested in native trees, I would recommend "Native Trees for North American Landscapes" by Guy Sternberg with Jim Wilson (the Victory Garden guy).
For container gardeners I like "Container Gardening" by Jim Wilson.
And, for just pure entertainment and enjoyable garden reading I loved CZ Guest's "Seasons of Gardening." Also like any of the garden books about Monet's gardens.
Coleen

Eddie:
That's a tough one because we live in areas with such widely varying climates. For example, up here in the far northwest corner of the country, the climate is much like that of southwest England, and Penelope Hobhouse's books and those of other British garden writers and designers are very useful to local gardeners. In fact, the book that first got me excited about new possibilities in gardening, back in the 1970s, was of British origin: The Color Dictionary of Flowers and Plants for Home and Garden by Roy Hay and Patrick M. Synge.

Among local books, I like Gardening with Native Plants of the Pacific Northwest by Arthur C. Kruckeberg and Landscaping with Wildlife by Russell Link. I have learned a lot about living in harmony with local wildlife from Wild Neighbors, The Humane Approach to Living with Wildlife by The Humane Society of the United States. Other sources that have been very helpful are the memoirs of American pioneers. Gardening in the Pacific Northwest started at fur company forts on the Columbia River in the early 1800s and spread north and south from there. Since my garden is [mostly] organic I have learned a lot from the trials, tribulations, and successes of our early gardeners.

My garden library has a large number of books on specific plants and topics, like Moss Gardening by George Schenk, Ferns for American Gardens by John Mickel, The Genus Hosta by W. George Schmid (as well as Mark Zilis's Hosta Handbook), Camellias by Jennifer Trehane, Classic Roses by Peter Beales, Bamboo for Gardens by Ted Jordan Meredith, The Tulip by Anna Pavord, et al.

I was also fortunate to pick up several older (1930s-1950s) garden and plant books at a local bookstore. I find these, too, very helpful.

Regardless of where in the country or world you live ...

"A Modern Tree Biology" by Alex Shigo a simple to read classic work and a must have if your into understanding trees and how to care for them .... the basis and motivation behind modern tree care ...

"Hortus Third" a dictionary of cultivated plants used in the United States .. a very big but expensive book .. but a industry standard reference ...contains a comprhensive glossary ... many accurate drawings and other references ...

"How To Identify Plants" ... HD Harrington ... a illustrated glossary of botanical terms used to describe plants ... can be used anywhere in the world. A essential reference for anyone that want to use the more technical plant identification guides.

For pure enjoyment, but not by any means "essential to a gardeners education", these are some of my favorites:
Hellen Dillon, Garden Artistry
Ken Druse, The Collector's Garden, and The Natural Shade Garden
Ann Lovejoy, The American Mixed Border
Tony Lord, Best Borders
Penelope Hobhouse's Garden Designs, and Garden Style
Rosemary Verey, The Garden in Winter
Ethne Clarke, Herb Garden Design

And if that doesn't kill your budget, there are many more.
I'm just reading Christopher Lloyd's Color for Adventurous Gardeners, he's always very entertaining.

For those of you in the far northwest there is a good book titled "Plant Life-Growing a Garden in the Pacific Northwest" by Valerie Easton. It is sectioned into months and has very nice pictures, also.

And, for pure enjoyment and wonderful imagination about how "your" garden could look, there's always any book written about Monet's garden at Giverny.