Just to echo what others have said, it is way better than it has any right to be.
The movie somehow manages to effectively capture the feeling of playing a casual campaign with friends. The story is played completely straight in-universe (as in, there is no outer-level frame narrative of nerds with character sheets gathered around a table), but you can just sense where the tabletop RPG tropes were woven into the plot.
Edit: also to clarify, the specific movie others are describing is D&D: Honor Among Thieves. Not any of the bad D&D movies made in the early 00's.