The Deeds of Paxanarion by Elizabeth Moon has a ruin exploration or 2 in it IIRC. Plus its probably one of the best DnD feeling books ever!
Deed of Paksannarian Book 2 is basically T1 converted to a novel. The NPCs are there, moathouse with bandits, and evil cleric of Lloth in the dungeons below masterminding it. The series is good with lots of D&D like exploration, including an adventure to find a lost tomb, and Paks imprisonment underground.