It's a sci-fi, fantasy, and murder mystery animated show, rolled into one. It tackles time travel, mental illness, and reality. Go in fresh — don't read any reviews or commentary, and commit to the whole season. The whole series is less than 3 hours, and comes into its own towards the end.
(Update, November 2022: Season 2 wasn't as good in my opinion, but Season 1 stands on its own just fine.)