Thanks, I hadn't seen bookbinder.js, that looks really neat. I'll remember that if I get back into sewn binding.

I personally like to use standard A4/letter size paper and print one page per side and do perfect binding. Printing two A5 pages on A4 was my original approach, but then the grain direction is wrong for standard computer paper and the pages come out too stiff.

I think the quality is good enough for me, but I definitely understand the appeal of sewn binding.