Heinrich Cornelius Agrippa (1486-1535) is the most influential writer of renaissance esoterica. His de occulta philosophia appeared in three books. Written from 1509 to 1510 (he would have been 23 at the time), it circulated widely in manuscript form, and was eventually printed in 1533. It is a "systematic exposition of ... Ficinian spiritual magic and Trithemian demonic magic (and) ... treatised in practical magic" (I. P. Couliano in Hidden Truths 1987, p. 114).
Without doubt, this book should be at the top of any required reading list for those interested in Western magic and esoteric traditions.