What is the most difficult modern English book to understand?

[robert_columbia]

What is the most difficult to understand book, poem, or other document that is written in Modern English (yes, this includes Shakespeare and the King James Bible, but doesn't include Chaucer)?

1) Which is the most difficult because of fundamental language issues, such as archaic grammar or vocabulary, uncommon vocabulary (not directly inherent in the subject matter of the book, such as unnecessary use of "whereas" and "heretofore"), uncommon spellings of words, or long, complex and convoluted sentence structure?
2) Which is most difficult not because of fundamental grammar, vocabulary, or structural issues, but because the subject matter of the book is arcane to people today, such as a book on chivalry that is difficult to understand because it presupposes that the reader is intimately familar with the nuances of social issues involving nobility and uses vocabulary related to great country estates that is unfamilar to people today?
3) What recent (e.g. late 20th century or later) modern work is most difficult to understand because of required subject matter knowledge, such as a complex PhD dissertation or scientific journal article?

Is the answer different if you limit yourself to poetry, novels, scientific writings, commercial documents, or some other category?