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Maybe it's just a regional thing, but it's showing 78 euros for the paperback for me. Plus I bought the paperback recently at that price too.

For the ebook

Use FOOD30 for 30% off.

“The promo code "FOOD30" is not valid.”

Might be a region-specific promo code? Worked in the US for me.

Works only on the paperback. I had added the bundle to my cart.

With or without DRM?

It's available as a PDF. I think Elsevier puts the buyer's name (email address?) into the file as a watermark of sorts, but that is it.