Choosing just right books

Choosing a just right book for reading time is sort of like choosing the right shirt.  

This is a too easy book.  It is too comfortable.  The words are too easy with none that are tricky. 

 It may be very short with large text.  I might have read it many times already.

 This book is too hard.  It is not comfortable because it is full of tricky words I don't know.  I don't understand it.  

The text might be small and there might be lots of pages with few pictures.  

This book is just right!  It is not too easy or too hard.  I know most of the words, 

but there are a few tricky ones.  It is not too long or too short.  I can understand it.

 Thanks for modeling, guys!