book isn't big enough to have a Wikipedia article and I can't find a website with a summary, I ask ChatGPT to give a summary that includes a list of main characters with a description of them and a summary of the plot that includes the ending with spoilers. The results are often helpful but also spotty. For example, for one recent mystery book:

It said that one character was upset at the murder victim because the victim had previously raped this character's younger sister, which led to her suicide. This confused me because I had already read a few pages of book 2 and little sister is alive and well. I then found a site with a summary and found that the rape also didn't happen

If that wasn't bad enough, the ChatGPT summary named the wrong character as the killer.

I found it helps to ask follow-up questions, but you need to be careful to not ask leading questions as ChatGPT will sometimes add things to the story based on your questions. I once asked something like "Was there a character named Allie?", and ChatGPT responded that there certainly was and gave some info on Allie. Spoiler: There was no Allie in the book.