Citadel of the Raven: A 5E Solo Gamebook

Publisher's blurb:

This is a Dungeons & Dragons Fifth Edition adventure designed for one level 3 player, without a DM. It can also be played by two players without a DM, as a DM+1 adventure or even as a full DM-led campaign with multiple players, but it is primarily designed for a solo player. The written narrative entries in this book serve in place of the dungeon master and guide you through the adventure.