What would be a good way to bind a A8 notebook? I would like to make a A8 notebook (52mm x 74mm) with about 50 sheets or more, but I'm not sure which binding would be the most suitable to use. 

I generally use the Japanese binding for my A4 notebooks but I don't think it would be the best choice for something as small as A8.

I would like to keep it as simple as possible, since I don't have proper bookbinding tools (and the suggestions I've found on the internet all require some sort of bookbinding tools for a decent result).

The cover material doesn't matter (although I'd probably go for transparency sheets, since I have some around). As long as I can turn the pages and use a good amount of their space anything would do.
I ended up using the coptic binding and it went surprisingly well. The only thing about it is that (unlike the Japanese binding) it needs something to hold the notebook close (but it has 8 x A4 sections, after all). It seems that, being similar to the coptic binding in a way, the section sewn hardcover binding would have also been a good choice. Contrary to what I previously thought, not having special tools does not seem to matter for the final result.