I'm enjoying Spiritual Tarot: Seventy-Eight Paths to Personal Development by Signe E. Echols, Robert Mueller, Sandra Thomson.
I'm about half-way through it, and I like:
-- the personal growth perspective.
-- the fresh take on keywords.
-- the discussions of colors and symbols, without getting overwhelming about it.
-- observations on 3 different decks: Rider-Waite, Morgan-Greer, and Aquarian. If you've been working with any of these decks for a while and feel the need to go deeper, this book may be what you're looking for.