As someone who thought the same (stock was enough for me) until I had some free time and switched, here are some things I'm really enjoying, in no particular order:
- Format support: EPUB, CBR/CBZ (comics, graphic novels), PDF
- Dark mode
- Fully programmable gestures and shortcuts
- Automatically syncs with my readeck instance (think readitlater/instapaper) to dowload the articles I save for example here on HN
- Calibre integration over wifi
- RSS/Atom
- Custom dictionaries
If you are into manga, there is an extension for directly downloading them on the device
- Format support: EPUB, CBR/CBZ (comics, graphic novels), PDF
- Dark mode
- Fully programmable gestures and shortcuts
- Automatically syncs with my readeck instance (think readitlater/instapaper) to dowload the articles I save for example here on HN
- Calibre integration over wifi
- RSS/Atom
- Custom dictionaries
If you are into manga, there is an extension for directly downloading them on the device
I'm really happy I made the switch.