Hello, I suggest on having it available via the web version in the future as well and if you are open to it, then open sourcing it as well.
This can do some wonders for a review app.
Books also have bar-code so it can also work as something like scan the book's barcode and then review the book or find community which talks about the book (I am imagining then an discord/telegram/whatsapp like interface where people can chat too)
So we scan bar code of a book, then we can join a channel where people can just talk live and make connections from the book.
This will definitely have people who are fed up of social media as-is and want something more niche but unique/authentic so its kind of good on that ground!
A bit tangential but actually I have a domain which I bought called k4qr.com, you mention that qr codes also work, so perhaps you can rename the app as Kodala (with a K) and I am happy donating my domain to you as well for your project, let me know! (funny story but I was actually wondering myself when I had bought that domain if I should do something qr related with that :-] )
Actually another thing but also allow text as input too for web related things for example. I am imagining what I might want to use your product for example.
So I go to your website and just write something say game of thrones and it can show some books or tv show qr code which anybody has scanned and I can click on any of that too and then I can land in their social media and talk about game of thrones
Now you can also do it for something niche with qr codes, perhaps have an optional field, tags etc. that people can enter into qr codes when they first scan it so that people can search them
Just a few suggestions that I have, hope any of them might help you in a meaningful way.
Have a nice day.