Program once memory is quite resistant, and of course, plain old ROM is a rock, literally. Transistors do not deteriorate unless you use them, just like resistors and a lot of the available capacitors.
On how to operate it, it's an e-reader, you turn it on there's the manual there. There is the really difficult part of telling people "put 12V DC here, ground on the outside", but it's trivial compared to the problem of people understanding the books inside.
Since we're going through flights of fancy in these threads, another option would be to add a built-in solar panel to your hypothetical e-reader. Expose it to enough light (and you can probably assume the lighting won't be much brighter than a tropical midday sun) and it turns on.
Yes, but then you would both incentive people into placing your device under sunlight and need some of the shortlived kind of capacitors.
It should still be possible to make a solar powered e-reader long-lived, but a replaceable power supply is a good idea even if your device has to last for a couple of years.
But 21st-century ROM isn't human-readable without a 21-st century computer. Would that survive a millenium? It's not enough to have a storage medium that lasts 1000 years; the entire tech stack has to.
On how to operate it, it's an e-reader, you turn it on there's the manual there. There is the really difficult part of telling people "put 12V DC here, ground on the outside", but it's trivial compared to the problem of people understanding the books inside.