I've checked in cardboard boxes of books numerous times on AF/KLM flights and never had an issue. My only pieces of advice are to put twine or rope around the box so that the baggage handlers have something to grab it with or they're likely to be harsh with your box especially if you're close to the 23kg limit and more-so the 32kg limit for biz. Also you cannot use enough packing tape. If you think you've used too much, give it another 25% extra!

I've had a 32kg box that opened transit at CDG and came home in a plastic bag missing a few volumes... Since using rope, no probs...