I will admit there are some books that are extremely difficult to read but most times it is because of when they were written. For instance, Pride and Prejudice is a challenge to read if you are not used to the proper English they used back during that time. The book was written as a modern-day book for its audience which was for people during the late 1700s to the early 1800s at the time. This is the same when it comes to Alexander Dumas who lived during the early 1800s to the late 1800s. He wrote Count of Monte Cristo, The Three Musketeers, and other books that were difficult to read. Another big example of a difficult book is Lord of the Rings since Tolkien made up his own languages, wrote in an older style of writing plus based his series on the battle experience that he earned during WW1. There are more books that can be hard to read but these are the ones that come to mind for me.
Are there any difficult books to read in English that you have come across? What were they? What made them so difficult?