When Carl, began the first R.I.P. Challenge in 2006, I was all in. I think the last time I formally joined was in 2016 or 2017, but I continued to read spooky books during the fall. If you are looking for some suggestions, here are some that I looked back and found.
A list of some of the books that I'd read for the challenge posted in 2011
Almost anything by John Connolly or Sharon Bolton
I wish I'd kept better track of R.I.P. books, because it is such a fun challenge. At first, I concentrated on classics, then I moved on to some more contemporary books that fit the parameters of the challenge. I also read some middle school or YA that were good, too.
Now, I just look for what others are reading and add some to my list.
My favorite holiday is Halloween and spooky/supernatural books fit the season. I'm not quite ready to get the Halloween decorations out, but I'm certainly thinking about it. I just ignore the Heat Advisories and think pumpkins.
Anyway, I'm checking your R.I.P. book lists and stealing your suggestions. :)