@goinveg very amusing that you are looking at similar books. Having a chance to read them was a big motivator for buying an ebook reader.
@hyperb Based on Kobo's page count there are about 100 pages per chapter.
@Stinger regarding size of split HTML files. This was my first thought too. I had a big fight with Calibre (7.7) trying to make it split the files at 50KB. It kept splitting at 260KB anyway. I erased settings manually, reinstalled etc. Eventually I figured out that it silently ignores requested split levels below 100KB. Huge waste of time.
After at last managing to split the HTML at 100KB chunks (confirmed again by unzipping) the book now loads in a blistering.... 3.5 minutes. This is not an artifact of running the book through Calibre; I tested again at 260KB splits and the time went back to about 2 minutes.
I am really curious as to whether Kobo is unzipping the whole epub into memory, or unzipping individual files on demand. I also wonder how much flow calculation is being done on initial load.
I'm leaning toward splitting this book into 2 halves, but can't see how to do that with Calibre.
Any other ideas would be great.