but haven't played any of the others, is it possible to enjoy the game/not be lost without playing the other(s)?

Until Book 5, I would have said "Yes, you'll be just as confused as the ones who played the other two". :)

But fact is, the fifth episode/conclusion does its darndest to wrap up all the dangling story ends from Dreamfall, and the final scene can really only be understood and emotionally savoured if you've played The Longest Journey.

If you're not into 17 year old 2D point & clicks, The Longest Journey might not be for you, and if you're not into 10 hour cutscene fests with questionable controls, neither is Dreamfall.

I'd say go with your gut here. The whole experience certainly requires you to play the other two games, but no one says you can't enjoy Chapters because of the few question marks that remain for you at the end. And no one says you can't approach these mysteries in the order you want. You could play Dreamfall Chapters and then turn to the predecessors to get the full picture - that's all valid.

To be honest, I'd like an opinion from someone who plays Dreamfall Chapters first, then turns to the Longest Journey.: "Wwwwait, people didn't know THAT until 17 years later?" :)

The first game is still the best, even though it is so old:)