Each of them had a well stocked library, whether the nobleman was literate or not. Norway was much poorer, and had no such castles. This all meant that getting books was extremely difficult here. I think this traditional scarcity of books has made us more aware of their value. Norwegians seem quite traditional in their choice of collectibles.
Most people collect first editions of our national literary canon.
Henrik Ibsen, Alexander Kielland, and Knut Hamsun are the most popular. Apart from the literary classics, geneaology and local history are the most collected topics. Our preferences in books have remained largely unchanged since before WW II, but some of the authors who were popular 50 years ago have completely vanished from the market. Not even the canonic authors are immune to a merciless drift into oblivion. Bj rnson, who was once considered more important than Henrik Ibsen, is hardly collected by anyone these days.