Lexile measures the difficulty of books and your child's ability to read them.
A rule of thumb, is the Five Finger Rule, to have your child open a book to any page and read a whole page. This can also help the child know if they are interested in the book. If your child does not know 1 word it may be to easy, if your child does not know two words it is a good book, if your child does not know three words it's also good but it may be challenging, if your child does not know 4 words it will be challenging and they may need help, if your child does not know five words they need to find another book. If your child can read the word it does not neccesarily mean that they know what that word means.
Your child's Lexile score is found on their iReady score report. Their Lexile score tells you the level of difficulty and complexity of books your child can read.
Each book also has a Lexile level, their is an app which tells you the Lexile level of any book, called Level It Books.http://http://levelitbooks.com/
You can search our Destiny catalog in the library or at home to find books specific to your childs lexile range. http://http://destiny.richmond.k12.ga.us/cataloging/servlet/presentadvancedsearchredirectorform.do?l2m=Library%20Search&tm=TopLevelCatalog&l2m=Library+Search