Most people will barely read through a couple basics, so it can be a bit of a though sell to start recommending more niche stories. And part of the reason that some of these books are so successful is that they tend to have pretty widespread appeal, while more niche books will be more divisive and less likely to get recommended broadly.

If you're so well-read why don't you grace us with some of your non-mainstream S-tier recommendations?

From this list, one of the books that I recommend to everyone is Piranesi, which is fairly mainstream, and if they want to explore Russian magical realism then Vita Nostra. Unsong is another favorite. In general I love to explore magic systems that experiment with breaking a system, or stories that explore how different rules might interact within a system.

I think people sometimes underestimate the value of lighter more fun reads, like cultivation stories. The best western adaptation of this style of novel is probably the Cradle series, by Will Wight. Even though the stories tend to be fairly light, they're quite enjoyable for exploring new modes of thinking. For example, we can analyze the interactions of energy as an abstract / symbolic form, and how it influences human behavior; which is an abstract / symbolic application of the cultivation lens over reality. To give an easier to understand example: Feng Shui isn't real but it's true, in the sense that the way in which we organize furniture within a space determines how people navigate it and how they interact. And why might this be useful? Well, sometimes we fail to see the full picture when using a single lens, and different lens might let us see things in a new light.

I've read some terribly generic web novel slop and gotten fairly unique and interesting perspectives from them, but most people aren't good enough readers to enjoy bad books, so they can only read and enjoy good books.