(just kidding!) You know, those Lemony Snicket books might be a good place to start because it constantly introduces vocab and you can work your way up
Most chapter books are good and thick books too. It's about reading a really wide range because different authors have a different way of writing. Shakespeare uses old English and some pretty uncommon words. Rick Riordan (Percy Jackson author) uses more modern English. Authors such as Paul Jennings and Andy griffins, write with common words and a few harder words. But I would recommend reading the Eragon books by Christopher Paolini. I hope I've helped.
參考: My own knowledge as a published writer and I love to read. :)
Just read any genre of books,read the newspaper,even comic books have been shown to be written on a 9th grade reading level.Open the dictionary to any page on even number days and pick a word.This week my words were xebec and piqued.Also refer to a thesaurus.Then main thing is to read with a voracious appetite and thirst for knowledge.