Here is mine (for fiction):
1 star - truly terrible, little or no merits. not even so bad its good kind of bad. Will most likely drop the book. Whether we should even rate books we haven’t finished is another discussion. However, I am of the believe if a book has nothing going for it even though you’ve read 100 pages, it’s probably a 1 star.
2 star - it was ok. Enjoyed bits here and there. It did not feel like a waste of time, but would not read again.
3 star - this one is hard to define. it was better than ok, but not great. would probably not reread, but fairly enjoyed.
4 star - very enjoyable, would not mind rereading. maybe there were a few flaws here and there, but nothing detrimental.
5 star - this book made me think about it for days, weeks, maybe even months. I care about the characters like they’re my own family. I would want to reread it again and again. Although, there are some books I would not want to reread, maybe because it dealt with dark or violent topics, but I would still rate 5 star because of the impact it had on me. Did the book change me, did it make me want to reread it, those are pretty good criteria for me to see if the book deserves 5 stars.
Note, I have never really rated books until recently. I realize it helps me reflect on how I feel about the book, and helps me get closure and move on to the next book without any unnecessary lingering attachment. Unless its a 5 star of course, then I’ll think about it forever, haha. I don’t even have a goodreads or do reviews or any of that jazz, just thought it would be fun to discuss.
I’m fairly simple: if I get to the end and I’m sad there’s no more to read, it was one I liked. I’ll probably reread the entire series fr scratch at some point in the next year.
One trilogy I recently read I was happy to get to the end because it looked like they were never going to explain wtf happened in any of the books. Good, it’s done, they don’t explain, I don’t really care. When I looked back, I was mainly reading for an explanation of wtf is going on (it’s a guy existing in 2 different worlds, switching when he goes to sleep), and never got it. I hear there are more books in the series to read but I’m just not a fan after the first 3.
The only real exception was a series by Brent Weeks, which I loved when I first read, but knowing the what and how of the series makes me too sad to reread it and get invested again, because some stories hit you in the gut. I’m hoping one day I forget the ending and can enjoy it from a fresh perspective again.