Reading back, I noticed posts about the book of Kells. High res pages are available online as well, I do Kells style art for SCA awards.
I can't, even with modern tools, figure out how on earth they managed some of the details. Some details are so fine that they require magnification to see, and yet it is believed that magnifying lenses hadn't been available in Europe at that time.
I have seen a very interesting interpretation where someone made a book of Proverbs (the Bible book) in the Kells style.
I'd be thrilled to have a Kells reproduction, but my second choice would be the Red Book.