Subtle difference in English: heavy reading or dificult to read.

Question

Este libro es ________. This book is difficult to read.pesado leerpesado leyendopesado de leerpesado en leer

In English, we also say that a book is "heavy reading" when the subject matter is academic or complicated and detailed. A subtle difference between heavy reading and difficult to read. A book might be difficult to read if it is badly written. Not quite the same as "heavy reading"

Does the same subtle difference exist in Spanish?

Answer

Hola Ian,
The only thing I can think of in Spanish for a "heavy reading" book is saying something like "Este libro es muy intenso."; that would mean the book has information that is difficult to digest, the story is too complicated, or for example it is too technical and your brain needs to work a lot to understand what it is written. 
Inma