After stumbling across the castle quite by accident in the early 1970s I found the fascinating book about Enguerrand de Coucy VII by Barbara S Tuchman a few years later. I've probably read it half a dozen times over the years. The first 2 visits were in glorious Picardy sunshine, the last in August 2015 was in lashing rain and howling wind.
It was the visit I enjoyed the most! I can't recommend a visit here highly enough if you've read the book. I notice there have been a lot of improvements over the years with information boards and new areas open to visit. In July there seems to be a fair and Son et Lumière type of "spectacle" on several evenings.

If you haven't read the book but you have an interest in castles and medieval Europe look up "A Distant Mirror: The Calamitous 14th Century" by Barbara S Tuchman. It's available on Kindle too. Then go visit the castle.

Ruined Chateau with interesting history. Takes about an hour. About 5 Euro for adults and kids free. Was interesting to contrast with Chateau at Pierrefonds about 40 mins away.

Once the largest fortification in Europe and sadly ruined by the Germans at the end of WW1. An amazing building!