In any case, his is the more difficult book to put down.

We will see what happens when she encounters some of the more difficult books.

He felt that it was a difficult book to release.

I have heard it is a very difficult book!

It was worth the effort, but that is the most difficult book I have read.

First let me say that this was a very difficult book to write.

It is a very difficult book, even for the German reader.

A difficult book in some ways, did you find it difficult?

For example, read a difficult book or balance your checkbook.

This makes a complete translation of the book very difficult.