From publisher blurb:
Appendix D is a huge supplement for Dungeons & Delvers: Black Book that adds five new races, eight new classes, more talents for existing classes, and more crafting examples (both materials and what you can make with them), monsters, and magic items. It bundles up most of the content from the first six Appendix D "zine" PDFs (included for free with Black Book), along with some new stuff (like the sorcerer and paladin classes) and a bunch of original art (over 40 original illustrations).
There's also some tweaks to most of the original classes and some of their talents, and how weapons and armor works, rules for encumbrance, universal two-weapon fighting talents, optional rules for rolling up 0-level characters, backgrounds, random WP and VP, multiclassing, and abstract weapons and armor, ways to change healing and initiative, a pretty intricate series of tables for gems and art objects, and some suggestions on how to handle stuff like stacking resistances, charms, and healing unconscious characters via magic or alchemical potions.