Made in Abyss is going down as one of my favorite shows of all time. Not just one of my favorite animes, one of my favorite shows. The characters, world-building, plot progression, music, art style, animation, voice acting (sub and dub), everything is incredible.
The show is a return to fantasy elements, and doesn't set up an rpg style world or borrow from Tolkien or C.S. Lewis. It begins in an optimistic and lighthearted tone with just enough dark implications to get you wondering, but as it goes on it begins to explore the most brutal aspects of being human in an increasingly harsh manor. But it never gets to be too much, and it doesn't feel like gratuitous suffering because the two lead characters push through with hope, determination, and a childish charm.
I really hope Made in Abyss gets another season. I'm dying to know what happens after the latest episode, and I would read ahead in the manga if the author weren't such a creep. If you're prepared for a shockingly dark and intense show with incredible quality and enough high moments to get you through the low ones, then give it a watch. You won't regret it.