The difference from if I had to buy the book online would be measured in terms of time, physical move and money.
Indeed, with the digital purchase, I spent less time buying a book. If I know all the information about the book and that I have my credit/debit card with me, in a matter of 20 minutes the transaction is done. However, if I had to purchase the book using the analog setting, I would either walk or ride a bus/train/taxi or drive to a bookstore depending on its location from where I was when I desired to buy the book.
Moreover, an online purchase hardly requires movement but gestures, unless I would work to the mailbox to draw the book from after it was dropped. In the case of an analog purchase, I would anyway do some exercises, including walking and/or driving. And, depending on the distance, I would put some time to get there, though there would be a great benefit if my daily activities were typically sedentary.
Furthermore, both driving and riding a bus/train/taxi to get to the bookstore would cost some additional money. There would be a financial aspect too in using shoes and cloths, which would need to be washed up. In addition of all of that, a book is more expensive on a shelf than it is online.
However, a way that an analog purchase might catch up over its digital counterpart in terms of time is when a mistake is committed during the process. I would go back immediately to the bookstore to fix it and still have my book the same day; what is not possible in most digital purchases where I would have to mail the book to Amazon, which would send me a new book or my money back within at least one week. Unless, not only the purchase, but the product also, was digital, such as a kindle version.
Through my example, going to the bookstore where I was able to use physical money to buy a book is analog. So would be the face-to-face seller-buyer interaction as well as the physical activity that required. However, buying a book or any item from Amazon or across the web is digital even though I note a kind of cohabitation analog-digital in my Amazon purchase. I touch my book, and it is made of analog operation, which makes it remains analog. An audiobook would be a totally digital operation.