I just added the book about De Brassers https://www.bookogs.com/book/486090-de-brassers
I used Paperback as format, but I'm not sure that's correct. The book looks glued together, not really like a paperback.
Also, some parts are in Dutch and some in English, so I added both, is that OK?
I wouldn't get too excited about using Paperback as it probably describes the format adequately. The alternative is Soft Cover, but it is up to you.
The way you have listed the languages is perfect as that is how a previous Forum discussion agreed to list multiple languages: in alphabetical order and separated by a comma.