Look on the cover/inside the few front pages of the book. If you can't find it stated on/in the book (not all books will say), try a search for the book online (check the publisher's website?) and hopefully you'll find what you're looking for.
If you're looking for books at a certain level, a simple Google search should find what you're looking for.
Addition: Lots of schools use the Accelerated Reader program which gives reading levels to most books so that kids can test appropriately.
Try reading the book and the answers will be there.
I need to know where I can find the reading textbook.
Try reading it and find out. (:
Look in the book/reading sections?
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The Twilight Saga isn't a ver high reading level, but it is a book for mature readers. The Host is also a good book by Stephenie Meyer. There is also Prom Nights From Hell.
bookwizard.scholastic.com has a search to find grade levels for books.
When looking for a book reading device there are many to chose from. Do your research to find the one that is best for you at eBook-reader-review.toptenreviews.com
http://www.scholastic.com/bookwizard/ will let you find books that fit their reading level, and as they progress in reading levels, you can order more advanced books.
By reading the book.
All books have words in sentences. Just open the book and start reading.
I have searched and there is no book by this name. Perhaps there is an expanded name to the book? Try Amazon.com to find the book you are interested in. Happy reading!