Build a 3-book “Mission” series first (not standalone)
Adopt one recurring hero and a mission structure that can reset every book without resetting the reader. Keep the hero’s competence explicit in the series branding: examples that work in adventure packaging are “field archaeologist,” “salvage diver,” “mountain guide,” “naval engineering officer,” or “military recon specialist.” Each book should promise escalating peril tied to a distinct environment: Book 1 ruins/relic retrieval, Book 2 jungle/wilderness survival, Book 3 sea wreck salvage or coastal disaster. This gives you a clean catalog story for readers and helps retailers place your title under the correct host shelf based on cover and keywords.