Old-School Essentials, subtitled "Retro Adventure Game", is a line of books released by the indie publisher Necrotic Gnome in 2019 that is a restatement of the Basic and Expert Sets produced for Dungeons & Dragons by TSR in 1981.

Writing for Dicebreaker, Maddire Cullen found the "old school" rules for D&D liberating to some extent compared to the modern Fifth Edition.

But Cullen warned that without pregenerated skills and feats to fall back on, "This all immerses you in the fantastical world that you’re inhabiting, but it definitely takes a while to get used to putting your character sheet aside and delving into your imagination instead."

Lines also noted, "OSE couples this faithfulness to the B/X rules set with an incredible layout that makes it quick and simple to look up anything that you need to during play."

Thrower noted that this was a "restatement" of the old B/X rules, saying, "There is nothing new here at all, just the previous text carefully combed and untangled of contradictions and confusions.

"[5] In his 2023 book Monsters, Aliens, and Holes in the Ground, RPG historian Stu Horvath commented "This is a work of extensive renovation.

Horvath concluded, "No other set of rules, including the current iteration of Dungeons & Dragons, is so clear or easy to reference.