kobo app v kindle app or reading on KF - I have still not decided which app I prefer or if they are so similar that it's not worth thinking about- so I am undecided which format to use for sideloaded books. My calibre library is mostly epub.
I did not like moon+ reader. it seems to ignore the books own CSS & does its own thing based on its own preferences. & it takes more + less intuitive taps to get to a TOC.
One advantage? of sideloading as AZW is that the book cover also then appears on the KF front page carousel. and in the books tab, whereas epub covers are not visible outside of the Kobo app.
I'll have to read up more on calibre content sever; as 1st look it does not solve my issue of retrieving a book onto a tablet without getting out of bed at night, when household PCs are asleep. The tablet can fetch from dropbox assuming I can remember the authors first name & find it library folders. I could dump the entire library onto KF - there'd GBs to spare on there, but then I'd have to learn how to do collections etc on KF which I understand is a pain to master.
( I am an old dog who likes to learn the occasional new trick - but s l o w l y - and not too many at once

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