I used to read a LOT when I was younger, talking about prolly multiple books a week, maybe even a day. Then stuff happened and I kinda lost it, but now Im getting back to reading and have been reading often-ish :) I wish I read more though, since Im obsessed with buying books lol, I currently have several unread books and just ordered four more yesterday....
I mostly read similar stuff to when I read younger (like ages 9-13? maybe?) even though Im 18 now, but its ok I enjoy the fantasy etc books :)
Some recommendations are Survivors (bc you mentioned Warriors lol),
and all the "basic" stuff: Percy Jackson (and other series by Rick Riordan), Maze Runner, Hunger Games, Divergent, Harry Potter etc
Then some that I havent really seen people talk about:
Half Bad - a trilogy + a short story, its about witches but is also a bit hard and emotional to read (CW: it deals with racism)
Fablehaven - 5 books, fairies and other mythical creatures!!
The Books of Beginning - a trilogy (Emerald Atlas is the first book), though I have only read the first two yet, it has magical books :)
The Thirteen Treasures - a trilogy (+ a short story which I only recently got to know of so havent read), more fairies!! One of my fave trilogies!!
Vampirates - 6 books, the name is pretty self explanatory.... vampire pirates!!!
I also have some like, single books, but decided to recommend these lol. I have more series too but many of them I dont think are available in english so rip
Also sorry for the long message, I like books and get exited when I get to talk about them lol
(Also SherbetToons , I think the "reading books makes you smarter" is because your brain is a muscle and it gets trained by doing stuff, for example reading. Plus fantasy books can teach about real life stuff too, and reading in general can make your language skills better. Though its true it wont really make you smarter than other types of media engaging as you said ^^ also, if you need visuals, graphic novels are great too, for example Heartstopper (def recommend!) that recently got really popular! /lh)