I love old books. I love the kind of old books you get at antique bookstores or on the Internet Archive. And I have a good collection of old books about Denmark.
I like old travel guides, most of which are still pretty useful because the Danes don’t tear a lot of things down the way they do, in say, Los Angeles or Hong Kong. In Denmark you’ll pretty much find most castles and monuments right where somebody left them hundreds of years ago.
If you want to see a famous church or square or the Jelling Stone, your Baedecker guidebook from 1895 will work just fine for you in most cases.