The e-mail was dated Monday and it said "all week on the website" and "this week only".

I forgot until Saturday and I did think it was a bit of a grey area because with the "can I have my extra book" comment I did write "if this is still valid". They said their week is the week when the shop is open so they didn't get my order until this morning and that's too late. The problem is that they think they are a physical shop with proper doors and opening hours and I think of them as a 24 hours a day website.