I'm planning to buy a few manuals for Chaosium's Call of Cthulhu, but I can't find anywhere if the other manuals (say e.g. Cthulhu by gaslight) and adventures are strictly tied to an edition or if they can be used without major problems with any one of the seven editions.
I see in this question that the differences between editions seem to be minor, but there are also cases where a new edition comes with incompatible rules, e.g. D&D, so I'd like to be cautious before I waste money in books I don't need.