I figure this may improve everyone's corona lockdown experience so here goes
Bookerly and Literata fonts are Amazon and Google products, they are specialised fonts for readers with e-ink displays.
Blog post about the advantages of these two fonts
Download Literata and Bookerly fonts
Now to install them, connect your Android reader by USB to your PC. It should show up as a device in windows explorer or any other file manager.
Then you copy the unpacked font files to the "Fonts" directory in the reader main directory. If the Fonts directory doesn't exist you have to create it. It should probably also work with a Fonts directory on the SD-card.
Reboot the reader and the new fonts should be available to the Android system and in the reader settings!