From publisher blurb:
Ever rolled a natural 20 or a natural 1 on an ability check and wished you got something a little extra for your great (or sometimes bad) luck? Then look no further! Fully compatable with Level Up: Advanced 5th Edition, Paradigms of Skill gives 19 of the 20 skills a fully-fleshed out pair of d6 tables for critical successes and critical failures on ability checks, expanding on the original tables found in the Adventurer's Guide. Dazzle with Performance or stellar Persuasion, or fall flat on your face if you fail your Acrobatics check—there's a result for nearly every situation.
Note: Medicine had its own dedicated table in the Adventurer's Guide, hence why it is not included in the updates. It, and the Arcane spellcasting critical success and failure tables, are reprinted in this book for ease of reference but otherwise are unchanged from their original forms.