By "little" I thought it would be brief, which I think it sort of is. But what it really means by little is that it is optimized for little screens such as a smartphone.

Go ahead and open it in your phone. You'll be delighted to read it.

Question for HN: how can I convert my existing PDFs and eBooks that I can easily read from my phone?

For e.g., I have a lot of Math textbooks in PDF format and I would like to convert them into a format similar to this deep learning book. How can I go about doing that?

koreader has a pdf reflow mode