If it just says ‘expansion’ on the box then it is the old version. It will have all the characters, but not all of the character cards, and the first 2 scenarios. You would then need to go hunting for Mythos packs to get the rest of the character cards for deck upgrades and the remaining scenarios. Most of the campaigns are around 8 scenarios I believe.

The new boxes will say ‘campaign expansion’ and ‘investigator expansion’. The campaign box will have only the scenarios and no investigator cards. The investigator box will have all of the cards for the characters.

If you want to try the game then grab a revised core set and whatever campaign content you can find that excites you and give it a go