Suspicion of terrorism, or nothing at all. If the libs are right they wouldn’t care about charges anymore. But since libs are so rarely correct, the government can hold you for 72 hours without charge and the patriot act has a whole list of charges that require no evidence for an arrest. Also statistically you live within 100 miles of a US border if you’re in the US, meaning border patrol can arrest you for any reason or no reason indefinitely.
Kindle paper works well, since you can just sync books into it with calibre or other software. They’re also amazingly tough to break in my experience.