I’ve started a series I call ‘passports to’: A6 size, i.e. passport size – thin enough to go in a standard envelope for 50 cents NZ. They are cute, and readable because they’re short enough to retain a standard sized font.
It doesn’t give the same scope for carved edges etc, but the covers could be embossed, and the paper special. I already do blank notebooks like that:
There may be a case for more passport-sized books, condensed for the modern lifestyle where space and time is so short…
Also it is traditionally a nice size for special little sacred books like meditations or short tales or sermons etc. One of my most valued books when i was a teenager was ‘The Greatest Thing in The World’, an inspiring sermon on Love. It was blue,thin, and smaller than A6, given to me by mum, and it changed my life.