ANSWER - There are more books written on witchcraft than you could read in twenty lifetimes. These range from obscure classical texts to modern 101 type everything under one cover books. Very few books have nothing to offer and very few books will give you anything close to a comprehensive understanding as an isolated read.
Here are some good basic beginner books that will get you started. (Links to Amazon). I've chosen these because they are all very easy to get hold of and cover a broad range of different topics and ideas under one cover.
Buckland's Complete Book of Witchcraft Raymond Buckland
Mastering Witchcraft Paul Huson
Hereditary Witchcraft Raven Grimassi
A Witch Alone Marian Green (More Wicca focused)
Witchcraft Theory and Practise Ly de Angelas (Very Wiccan though she thinks she isn't)
A lot of witchcraft and occult books are in the public domain and can be downloaded for free.
Try these sites for a wide range of free books.
Hermetics Witchcraft and Wicca Library