There is no universally agreed-upon definition of magick. In the broadest sense, Magick is any act designed to cause intentional change. One popular definition is “the Science and Art of causing Change to occur in conformity with Will” (put forth by Aleister Crowley). Some see it as a change in external reality, sometimes internal reality (perception or worldview or consciousness). Magick can also be defined as any of a variety of life-practices which devote the practitioner to self- and (thereby) environment- transformation.
Asiya has a huge collection of magical books, stored in the Magical Athenaeum and all can be downloaded as PDF. Great ressource!
Aleister Crowley: Magick, Bd.1 • Magick, Tl.2
Magick and Thelema