Liber T (and Tabula Mundi)
When I picked Liber T up on the trade train, I only knew it added unusual imagery to the Thoth minors, but thanks to reading Scion's work yesterday, I now get that a lot is pulled from decan descriptions in Liber Hermetica, Picatrix, etc. I would've been scratching my head without that help!
The art in my every-week deck, Tabula Mundi, is also inspired most obviously by astrology, but in TM, decans decide which majors will be reflected in the art of a minor, and which minors show up on courts.
I didn't get into the Thoth and later TM out of any love of astrology, even though it's central to them. I'm most interested in the way they deal with the Tree of Life and the idea that all things are actually one. Really Tarot of the Sephiroth, whose art highlights Kabbalah more than astrology, should be my favorite. But the symbolism and interaction between majors and minors in TM keeps it #1 for me.