Dungeons & Dragons is more popular today than it was at any other point in its 30 year history.
Wizards of the Coast gave a presentation at the Game Manufacturers Associations' annual Trade Show in which they announced that 2017 was the game's best year in terms of sales.
While specific sales figures weren't given, Wizards of the Coast noted that 8.6 million Americans have played Dungeons & Dragons over the last 12 months. In addition, over 9 million people have watched D&D games online via Twitch. Sales for the game's Fifth Edition content are stronger now than when the new edition first came out in 2017.
Dungeons & Dragons has experienced new found popularity due to a variety of reasons. The game's Fifth Edition ruleset is tailored to new players and contains simplified rules and game mechanics. Stranger Things also prominently features D&D and has used the names of various D&D monsters for their own antagonists. Finally, podcasts and shows like Critical Role provides entertaining live content that encourages viewers to form their own party of adventurers.
Wizards of the Coast's claims line up with D&D's strong performance on various game sales charts. According to the gaming trade site ICv2, Dungeons & Dragons was the top-selling RPG in fall 2017. Various D&D themed merchandise also made appearances on ICv2's top-selling "Card & Dice Games" charts, the top-selling miniatures chart, the top-selling "Board Game" charts, and the "Top Collectible Games" charts. Basically, Dungeons & Dragons is a super-hot brand right now and there isn't any signs of the game slowing down soon.
Dungeons & Dragons has a big 2018 planned as well. Their new publication Mordenkainen's Tome of Foes will expand both the lore of the game, add several new playable races, and give players new monsters to battle in adventures. Popular races like the drow and the eladrin will make their first "official" appearance as playable races in the new book, which should give players more options to choose from when creating their character. Dungeons & Dragons has two other projects on the way too, including a new Adventure for players to explore. More information on those publications are expected later this year.