Classic Fantasy will take your d100 games and allow you to turn them into a D&D inspired game, but you will continue to feel as if you're playing d100/brp games. Built as an overlay for the Mythras system (the updated Runequest 6), Classic Fantasy has replaced the Cultures and Careers with Races and Classes, though humans maintain the classic Barbarian/City/Nomad/Primitive mix. In terms of complexity, there is a new layer of play that is added upon Mythras, but for those either transitioning from D&D to BRP games, or for those looking to recapture some of the fun of those style of games, many of these features will feel familiar and sensible. The magic systems have been completely reworked as well, and there's an updated bestiary and treasure guide in the book. It reads nicely, and has elements of the fantasy "Greymoor" setting included in the book. An expansion book has been released that details later level play, and opens the scope. I have run an entire campaign with this book (and Mythras) only.

This book feels not only like a rules toolkit, but a loving homage to masters Moldvay, Gygax, Arneson and others.

Fair disclosure, I have done some writing for this system, not published at the time of this writing, but was neither asked nor encourage to review this product.