It is really all you need for a basic e-reader. However, I am not convinced that it will survive feature creep.

Esp32 runs out of headroom extremely quickly once audio processing (TTS) and screen annotation/highlighting are involved. Especially if they are implementing high quality partial refreshing.

I hope they can stick to the basics and make it a great, polished software experience because that is probably be the difference between failure and success of it, not featute-packing.