Always respect the 'fragility' of books; they deteriorate over time.. their construction and materials are susceptible to the conditions and handling they are under. Biblio, a book search engine, provides a list of cleaners; the article, at this time of writing, applies to non-leather books.
A good rule of thumb is this: Surface dirt can always be safely removed, if it’s removed by the least-abrasive means possible.
(https://www.biblio.com/book-collecting/care-preservation/cleaning-books/)
Although The Book Bug blog is written to schoolkids, their pair of free bookmarks on taking care of books should work with all reading children. You can download them at the Teachers Pay Teachers website.
(https://mrsnthebookbug.blogspot.com/2012/02/book-care.html)
Stores that cater primarily to large libraries should nevertheless be friendly to individuals as well. One such seller of library supplies on the internet is The Library Store. They offer a wide variety paperback book covers on its own dedicated page.
(https://www.thelibrarystore.com/category/book-covers)
The New York Public Library site has a one-page list of things to consider when taking care of your books at home.
