I'm not implying that 'quirky' habits are things done by only you. I just mean things you do or routines you have that are more involved than just reading the book and putting it on a shelf.
Here are some of mine:
For prose books, I put a page marker on quotes that really stand out to me (usually something that I relate to or believe in or something that really makes me think about life). I tried using a colour coded system for sticky tabs based on five categories (something like plot twist, romance, important info and I forget the others). I was inspired by someone on tiktok but categorising the sticky notes stressed me out so now it's just quotes I like. I also know some people enjoy actually annotating books and I tried that but didn't enjoy it.
For poetry books, it's similar but different. I put a page marker on poems that truly connect to me but I've recently started including post it notes on these pages outlining why I like these poems. Nothing in depth, just noting the imagery or lines I particularly enjoy.
This one will seem a bit odd, I think. Some people on the forum may know that I have quite a lot of signed books. I love signed books and some of them I've had for quite a long time so the spines are faded from the sun and maybe the cover edges are a bit scuffed or whatever. So now I have some books that I keep safe in the jiffy bags/padded envelopes they arrived in. It started with the signed hardback copy of No Matter The Wreckage by Sarah Kay my best friend got me for Christmas. Then I got my copy of Southwest On The A303 by our very own @Adam Gary. The I got Dimitri Reyes's Every First and Fifteenth. And now I have a few books that I refuse to take out of the packaging. (I did this with my signed copy of Evermore by Taylor Swift too.)
So what are some of your habits?
I love to go to any giant Barnes and Noble bookstore, browse the shelves in high interest areas (there are so many but poetry, self-improvement, natural medicine and nature are some favorites). I grab an armful of books and sit the cafe and speed read. It's a different kind of experience but I have plowed through many books this way. I also enjoy curling up with a good book and taking my time, but when I am in the bookstore I like to browse and then if after reading quickly, I decide I to buy the book, then I know I have a keeper.