If you are a player, do not read the module! But if you are a DM, the Tomb of Annihilation PDF is your best friend. The adventure is designed to be tough, and "save or die" mechanics make a return here. You need to be firm with the rules. The digital text allows you to double-check the wording of spells and magical effects that are suppressed or altered within the tomb. For instance, teleportation magic functions differently inside Acererak's lair. Having the PDF open ensures you don't accidentally allow a spell that breaks the dungeon's intended difficulty, maintaining the horror atmosphere that the authors intended.