... 'Books where a reader is one of the characters & takes part in the action'

It may start with 'You, your name' ( where you can put your real name while reading ) & the circumstances of the book plot you as yourself are a part of are given

or 'you are ( then some characters name and/or age is given ... for example 'You're a 16-year-old boy' or 'you're a '15-year-old girl' ( or any other age may be chosen for 'reader's character - I mean the 'character the Reader will be for the story - but it's not RP - it's a ready story where you can be either yourself or a character given by the book author ) 

🔷 Most of X Reader stories

- are about meeting some Singers, celebrities, movie or cartoon characters

- & some of those books may Contain Lemons 

( when this fact is not always stated in the title )

* & there can be absolutely Any Character X Reader books

you can find on Wattpad 

written by authors of various ages

( but most often Teens )

🔷 So if you are a fan of Any book, cartoon or movie character, some singer of other celebrity - you'll probably find 'X Reader' stories about them on Wattpad ( written by other fans )