You certainly can be a Witch without being Wiccan.
Witchcraft is basically a form of magical practice which someone of any religion or of no religion at all can do. Wicca is a specific religion which happens to include the practice of witchcraft. Some Witches do consider themselves to also follow a Pagan religion other than Wicca which they call Witchcraft, but Witches can be anything from Asatru, to Christian, to Zoroastrian or they can even be agnostics or atheists.
It's hard to find books on non-Wiccan Witchcraft but you might want to look at the writings of Laurie Cabot, Sybil Leek, and Ann Moura if you are interested in going further.