I've always had a soft spot for Doris Lessing's bizarre '70s sci-fi experiment Shikasta.
Ursula Le Guin wrote a review of Shikasta in 1979:
https://newrepublic.com/article/115631/doris-lessing-shikast...
I found this review really fascinating because I consider Le Guin and Lessing to be writers of equal caliber. Le Guin was pegged as a sci-fi / fantasy author, while Lessing just experimented with the form. (She won the Nobel Prize in 2007.)