Dholkey! One of my current projects involves working through the planets (classical and otherwise) in the same spirit as with the elements in The Elemental Magic Workbook. Overall The Planetary Magic Workbook will be heavier on Judaica and ceremonial magic, but will still address the planets in witchcraft, eastern traditions, and the chaos magic meta-paradigm. It will also explore potential magical applications of some fictional planets (such as Caladan and Arrakis from Dune, and Qo’noS and Vulcan from Star Trek).
Another more long-term project that ties in with this one is exploring the magic of the zodiac. Though a third book is a definite possibility, it is far off in the future and nothing has been set in stone yet.