A Bit of Electronic Advice

These days an enormous amount of old occult literature is available in PDF format. For ecological reasons, I'd prefer not to print out everything on paper, and it gets old having to sit at my computer desk rather than lounging on the couch, so I'm considering picking up some kind of electronic e-reader for the purpose. The difficulty, of course, is that I'm about twenty years out of date when it comes to technology and I have no idea what's available. 

What I'm looking for is a simple device that will allow me to read PDFs. I don't want it to be connected to the internet if I can avoid that, and I certainly don't want it to be dependent on one of the big predatory internet firms; I can get all the books I want from archive.org and iapsop.com, and I'm not averse from using USB drives to get them to my e-reader. 

Do such devices exist? Have you used one? Would you recommend it? Inquiring Druids want to know. 

(If I can get it used, that would be a plus -- I prefer to get all my technology that way, to keep things out of the e-waste stream..)