In the Netherlands, copyright expires 70 years after the author’s death in most cases. Many books published in the early 1900s and earlier are in the public domain. Here are five places where you can find these publications.
Delpher is a website by the Royal Library of the Netherlands where you can find books, newspapers, and magazines.
Digitale Bibliotheek Nederlandse Letteren
The Digitale Bibliotheek Nederlandse Letteren (Digital Library Dutch Written Works) contains many literary works from the Netherlands. Books can be viewed online or downloaded as PDFs.
Google Books has many Dutch books, sometimes digitized in collaboration with the Royal Library or other institutes in the Netherlands.
The Internet Archive has several public domain books from the Netherlands and many other places.
The Hathi Trust Digital Library has several books from the Netherlands and many other places.