easiest way to pick a good novel from a pile of unfamiliar books: choose the non-default authors
icon: "imperious (photo of me w imperious expression wearing "Red Queen" makeup: searingly red lips, darkened pointed eyebrows, black eyeliner, deep red & black eyeshadow accented with gold & silver, and black-outlined silver hearts & diamonds with red shadows on my cheeks)"
This is a great illustration of why I don't read 'classic' sci-fi. I also generally* do not read books written by defaults (straight white cis non-disabled non-poor neurotypical men), because they are almost guaranteed to be mediocre and full of Gary-Stus and women-as-props. There are some notable exceptions, such as Stephen Leigh (Mictlan series) and Nick O'Donohoe (Crossroads series), but generally, after a lifetime of being a default, you're trained to be terrible at perspective-taking which is the exact skill you need to write good characters. And when you never need to figure out your own solution to problems, you don't develop your imagination, so most aren't very imaginative either. (Alan Dean Foster is an exception to this -- wonderful imagination, sadly tainted by constant, condescending 'benevolent' sexism)
On the other hand, practically everyone else has to be exceptional in order to get published. Now there may be some who are exceptional only in who they know or how much money they have, but because it is so much more difficult to succeed as someone who is a person of color, female, trans, queer, disabled, etc, the available books are automatically higher quality than the average book written by a default (may not be true of self-publishing). And, as an oppressed and/or marginalized person, you automatically have more practice at perspective-taking, as you need it to live, so you write better characters. And if you have very limited resources, you have more practice at making shit work in ways it wasn't meant to, so you're more imaginative.
So the first thing I look at when I am scanning books at a used bookstore is the name of the author, and if available the author bio. Then I check to see who the main character is, and flip through the book until I see that person talking to someone else. By that dialogue I judge if the book is worth it. Most books will have a male main character who talks to other people like they don't matter -- instant nope. If the book has a female main character, I will scan to see if the dialogue centers around men -- if it does, nope. If the book has a main character who is neither male nor female I will get it regardless, because I don't get to see people like me in print and that is the closest I'll get.
When I am looking through books online, I look at the author first. If it's an oppressed person, I read the overview to see if the main character is a default: if they are, I won't read it (unless I already love the author) even if it is good because there are too many books with default main characters. If the main character is not a default, I look at the reviews. I look in positive reviews to see if anyone said that it made them realize new things or it kept them intently engaged, and I look in negative reviews for any criticisms that I consider legitimate, like a lack of thoroughness in world-building or rape being treated as titillating or harmless. Here is my wishlist of sci-fi, fantasy, magical realism, & speculative fiction by & about women & girls of color &/or trans/queer people -- I've shared it so that others can find good books without having to go through this intense process. I plan to add to it as I find new ones, so if you have any to recommend feel free (I'd love to add disabled authors & main characters). I also want to share a list of the books I HAVE read which are amazing, but I'm getting stuck on thoroughness there and finding it difficult to get started, because I want to do reviews of all of them.
I do still read books by defaults if they are exceptional and if they do not have a default main character (and sometimes even if they do); it's just rare.
[*]*this is not a hard rule across the board, and sci-fi/fantasy is actually better about this than many other genres. The only one which is a hard rule is that I will not ever purchase a book on self-help or spirituality written by a default, not even for ten cents. I consider such books to be somewhat blasphemous, due to so much desecration done by defaults. I feel that if a default genuinely wants to be a good person, they aren't going to profit off of self-help and spirituality. If they were giving away their book or making zero profit, I would take it and read it with interest. Otherwise they need to be silent. Their voices have been far out of balance for far too long and they need to not contribute to maintaining that imbalance.