This is the second 'small box' expansion for Eldritch Horror - I would compare this to the 'Forsaken Lore' expansion, which is the first 'small box' expansion.  Strange Remnants adds one new Ancient One along with the supporting card decks.  It also adds more cards to all the location decks, making all of those decks taller and increasing the variety of cards pulled during any given game.  Many would argue that getting 'big box' expansions like 'Mountains of Madness' (which I also own) is a better investment but it depends on your approach.  I do enjoy getting new side boards and so on but I actually prefer beefing up the base game mechanics with new cards to add variety.  For me personally I prefer 'small box' expansions as they add more to the base game without adding any clutter like new side boards.  Also, 'small box' expansions have a lower buy-in cost than 'big box' expansions.  To sum up, if you're an EH fan you probably already have this and if you're on the fence I'd say get it just to beef up the base game card variety.