I've used PIA for five years now. Never had an issue. It's plenty fast for my needs; I've seen sustained ~450 Mbps downloads from a transatlantic endpoint. (I honestly don't know what is typical with other VPN services but I'm not feeling choked out so I've never investigated.)
They run frequent deals and you can stack a promo code, check slickdeals and/or set an alert if there is not a current promotion. I believe my current three year sub worked out to ~$1.80/month. It is suspiciously cheap.
I'm sure others are "better" and "you get what you pay for" but PIA is good enough for the price for me.
You can sideload on to any kindle.
Paperwhite (non-SE) is the version to go for. They go on sale every month or two, check camelcamelcamel.
https://singlelogin.re/
https://calibre-ebook.com/
Have fun.