Buckland, Raymond. Buckland's Complete Book of Witchcraft. -- A step-by-step book for the beginning witch, but also an excellent reference for the experienced. Geared mainly towards covens, but adaptable to solitaries with some work.
------------- Scottish Witchcraft. -- Examines Pecti-Witan witchcraft. An excellent magickal-based system for those working in a Celtic background. Includes recepies and even a brief section on outdoor survival.
Conway, D.J. Celtic Magic -- A simple book designed to give the reader an insight into Celtic witchcraft. Has several good ritual ideas (self-initiation, and sabbat rituals), good spellwork ideas, and a guide to Celtic Gods and Goddesses. A good companion book to Edain McCoy's Celtic Myth and Magick (q.v.)
----------- Dancing with Dragons -- An excellent book on a little covered topic. McCoy give an excellent examination of Dragon Magick, from the types of dragons, to how to work with them.
Cunningham, Scott. Wicca: A Guide for the Solitary Practitioner. -- Probably one of the best guides for the beginning witch, especially practicing solitary. Cunningham makes the introduction to Wicca simple and intriguing. Includes a sample Book of Shadows to help you get started.
--------------- Complete Book of Incense, Oils, and Brews -- An incredible reference on how to make your own incense, oils, potions, powders, and so on. A great text for learning more about the techniques of original Craft of the Wise.
---------------- Encyclopedia of Crystals, Gems, and Metal Magic -- Another incredible Witch's reference book. Includes properties and correspondences for virtually every type of stone and metal out there.
---------------- The Truth about Witchcraft -- A fantastic book to give friends, family, loved ones, co-workers, etc. when discussing your beliefs with them. Almost essential when coming out of the "broom closet".
Kraig, Donald Michael. Modern Magick -- An excellent "pagan-friendly" book on ceremonial magick and basic cabala. Recommend buying the audio of the same name, unless you can pronounce Hebrew, Latin, Greek, and Enochian already.
McCoy, Edain Celtic Myth and Magick -- McCoy's book is useful on many levels for those interested in Celtic witchcraft. First, she provides many historical facts about the Celts. Second, she gives some incredible guided meditations in order to get into the mindset to work in this system. Finally, she includes a thorough encyclopedia of Celtic Gods and Goddess that the reader may come across in his/her work.
Starhawk. Spiral Dance -- One of the "Basics". Starhawk gives a view of eclectic Wicca as an alternative to modern patriarchal religions. Has excellent exercises to develop oneself magickally.
------- The Fifth Sacred Thing and Walking to Mercury -- Two fiction books by Starhawk, they depict the life and times of Maya Greenwood as she grows up during the 60's, her introduction to the Craft, and as she become influential in it in the post-apocalyptic 21st century. Great reading.
Ravenwolf, Silver. To Ride a Silver Broomstick -- An excellent book for the beginner on eclectic witchcraft. Silver combines an informal writing style and a common sense approach to the Craft.
---------------- To Stir a Magick Cauldron -- Magick Cauldron takes on where Broomstick left off. This book is written for more experienced witches who want to learn more advanced techniques. Know your stuff before picking this one up or you will be lost.
Various. Llewellyn's Magical Almanac -- Printed every year, this book contains information for every day of the year, including moon phase, astrological timing, and various correspondences for each day. In addition, it is packed with short articles from various Pagan authors and practitioners on a variety of topics.