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greml1n 's review for:
Dungeon Master's Guide
by Wizards RPG Team
A very good book, but not necessary. You can successfully DM and play without this book. I will say, however, that this book gives an incredible amount of tips and guidelines on how to run campaigns, make campaigns, etc. Most of the tips in this book can be found online on forums or in youtube videos, but all of the tips are very helpful.