B/X is good. When characters have d6 hp and it’s instant death at 0 the combat becomes way more serious and tense.

Project Gutenberg and librivox are decent resources for free older books. The author needs to have been dead for 70 years, so they are old but I’ve enjoyed “The Lost World” and “The hour of the dragon”

If you’re going to die, better to die on the main quest. I avoid side quest distractions.

The best lore is lore made at the table with the players. The rest is just gm inspiration.

Removed by mod

If you’re running a sandbox, you just need to review a bit ahead of the party in the various dungeons.