Try anything by Frances Yates. She is a serious and very respected academic historian, but she is also unusual in looking at issues around the interest in the occult and esoterica in the renaissance. Her books go in and out of print, but if you can get hold of her book on Giordano Bruno, or the one on the "Rosicrucian Enlightenment" they are both excellent.
Also, of course, try the TarotL online forum. It is probably the most heavyweight in terms of historical information. It can be a bit competitive in tone (one of the things I really like about Aeclectic is that it isn't) but some very good discussion goes on.
Hope that helps.