She stole that book...
Why didn't she just return it before getting in the truck? Why didn't the shopkeeper run after her?
" Benny, you silly great fat article"
The commentary on the American DVD (which my understanding is is different from the commentary on the Italian DVD) suggests this is just plain a plot goof.
It's relatively easy to rationalize it though: Emma's emotional state was so wrought at that time she didn't even think about having not paid for the book before getting in the truck. And the shopkeeper didn't realize the book she walked out with had come from the shop's stock.
BTW, according to the commentary, that book is fairly famous as supplying inspiration to high fashion design. At one point we are shown one of the pages of the book which is a woman in an odd-looking dress that includes a large and distinctive geometrically patterned cape over one shoulder. The dress Emma is wearing when she comes down the stairs to Edo's birthday dinner is a recreation of that very dress. Edo's flash of recognition when he sees the soup includes a lot of short flashback images such as his finding the lock of hair at Antonio's, and also includes both that page of the book and Emma coming down the stairs in that dress.
Thanks for pointing out that Emma wears a recreation of the dress shown in the book.
I don't think the book 'liberation' is a plot goof. As you say, she was in a state at the time. Also, she was so rich that the price of a book didn't mean a whole lot to her. (Granted, that's arguably over-analyzing on my part).
Shopkeeper didn't run after her: a) because he/she (I don't remember) was doing something else; and/or b) accusing the richest woman in Europe of stealing a book might not be so good to do. (There I go, over-analyzing again. But this is a really fun movie to over-analyze. I Love It!)