Well kids cant take themselves to the library, look online for recommemdations or take themselves to book shop.
So you gave to provide constant stream of books, imo kids who are bookworms are down to the effort parents put in.
I know parents who've tried and given the 5th book of a series and then when kid doesnt get into bemoan theyre just not readers. Things like that dont help, books should be read in order to get kids hooked into the characters and story as the author intended.
My tips are look at toppsta for ideas, kids can also have an account to review their books and enter book giveaways.
https://toppsta.com/
Use toppsta to find books by age or school year and use your local library website (if you have one) to reserve the books. Maybe go for the age or school year below to get them started and not too tricky. Make sure with popular series that you get the books in order, book 1, then 2, then 3 etc. If no library, cheap used books can be purchased via ebay or amazon but selecting the used option, normally for £2-3 per book.
Check if any of their favourite netflix shows are book adaptions as netflix went through a phase for a few years of adapting kids books so we tried many books that way.
And make reading non-negotiable, 20 or 30 minutes per day, with an alexa timer set, every day. The same mentality as brushing teeth is non-negotiable, reading is also non-negotiable.
So on appearance my dcs might seem like bookworms, but its been years of effort on my part doing all of the above.
Ive also done things like completed novels in exhange for say robox or vbucks for use in gaming so incentives can be used.
They want a new toy or gaming currency, I'll do that in return for 1 completed chapter book so they might choose to read for extra time to get through the book.
For that age my initial thought is graphic novels and things like dog man and bunny vs monkey but again research to ensure you get book 1's rather than dropping them in the middle of a series. But toppsta will see you right with ideas.
It takes lots of effort! Unfortunately theres no easy answer! x