Which e-reader should I buy?

I love to read from good old traditional paper books, but I’m coming around to see the advantages of also having an e-reader. I’d like a device that allows me to read outside and also at night in the bedroom (without disturbing my sleeping husband). I’d also like to minimize EMF radiation and keep the cost low. I don’t need a lot of bells and whistles (or any - none of my paper books have those and I’ve gotten along just fine). A long battery life would be nice. It would also be nice to place comments if I’m beta reading or planning to write a book review.

Is it risky to buy a used e-reader? If that’s a good option, where would I buy one?

Thank you for any advice you have time to give. This tech-timid gal is so grateful for her tech-savvy friends. (I’m moving toward tech-savvy, but there’s still a long road ahead : ).