I feel like the series ended on a metaphysical, non-solution. That's not a bad thing - I just mean there will likely be no definitive answer to Cooper's dilemma, and people can interpret it however they wish. It was an emotional ending, for sure. The final scene of Laura whispering in Cooper's ear, with that haunting music, will haunt me for some time.
But the grounded part of me would like more answers about the people of Twin Peaks and Mr C's endgame (which we never found out about). Why did Mr C seek the Experiment? What was he hoping to achieve, and what would have happened had he successfully found what he was looking for?
I hope The Final Dossier delivers on that, or at least infers something.
I don't think Frost would write the book if he felt there was nothing else to say about the events between Season 2 and 3. There's a part of me that feels much of Gordon's exposition in this series was paving the way for The Final Dossier.
Of course, I could be completely wrong. But this is my hope.
Bring on The Final Dossier!