(I had IFDB erase a nice long review--thanks!--so this is much abbreviated).
I played all four parts of Known Unknowns in one fell swoop and was to put it frankly blown away by it. I could see how it might seem a bit underwhelming serially but if you haven't had the chance to lose yourself in this richly imagined world, I highly recommend it. Set in the same universe as Bell Park Girl Detective and Birdland, I would say that Known Unknowns is the equal to Birdland, downplaying the supernatural elements to an extend and going deeper into the characterizations.
And the characters are amazing. A game like this lives and dies by the strength of its writing and it's probably not much of a surprise that Known Unknowns is running on all cylinders, with a gut-wrenching range of emotions with a HUGE cast. I'm sure you will find your favorites (shout out to my pal Olivia).
The game expertly switches from dialogue/conversation mode to exploration mode, as the two feed off each other.
Finally, this game is really really queer, and the range of people in this high school trying to figure their own identities out is tender, hilarious, melancholic, and ultimately human. And the choices you are given reflect that high school rollercoaster at every turn.
This game is a treasure and you should play it. It's one of the most affecting works of IF I have ever played, in fact.