I am convinced that Isaiah is a book written about the end times.
It's about Christianity and what happens to it.
I don't not see any reason to doubt its authorship in any way.
Another conviction I have is that it is the Jehovah's Witnessess who are fulfilling the prophecies in this book.
To begin understanding my conviction I recommend that you watch the video; "Jehovah's Witnesses Covenant With Death" which examines the prophecy in Isaiah Chapter 28.
http://www.youtube.com/watch?v=wFBXykSerq8
Everything the bible said would happen is really happening!
abe