Based on this blog post, except when I went to Salvos and Vinnies, I couldn't find a clutch in the same size as my thrifted book. Thus, I spent a good day sewing up my own wallet/purse inside. Unfortunately, as I still have a long way to go before my sewing skills are anywhere near decent, the overall effect was a lot less polished, but I value the final product so much more.
It's a pretty simple concept, but actually carrying it out took more effort and skill than I thought! For example, I couldn't cut out the pages of the book very efficiently - the 'stumps' of the pages are still a little uneven. Also, sewing card pockets in particular is very fiddly (which I knew from past experiences). Still, I'm happy enough with the way it turned out. If I ever find the time, I think I might make another one, and work on making it look more polished.
Sorry that I don't have any in progress shots, I was working as quickly as possible and I just forgot to take photos! I'm happy to answer any questions though :)