[diehunde]

Aren't most books single column layout though? If I have to read a paper I can use a tool such as k2pdfopt[1] and read it on my Kindle.

[1] https://www.willus.com/k2pdfopt/

[Libbum]

I mostly read scientific papers. Quite a good number of them are two column. Haven't come across k2pdfopt before - I'll check it out, thanks!