Searchers of the Unknown and most of its variants are incomplete in my view in that they (most variants included) lack a bestiary. The rules themselves, however, are well thought out and directly compatible with OD&D, so I have a bestiary! One page of rules works for me. If I were new to RPGs or was considering a non-D&D system, I would want mechanics, a small bestiary, notes on tech/equipment, a few spells, and a sketched setting (last priority). Something the length of TBH would suffice.