If you don't mind reading online
you can easily get free pdfs from Google Books, which also means you can see what they looked like shortly after they first came out; or...
If you don't have space on your device
for a lot of pdfs or one of your pdfs turned out smudged or something, a great deal of old books are available in HTML ebooks from Prodject Guttenberg and if you go to the top right corner of your screen and tap verticle ... you can add them to your homescreen. Adding shortcuts to your homescreen does not take up any extra space.
If you prefer Kindle
I advise looking ebooks up directly in kindle, and rather than in Amazon disambiguation, because sometimes you can't find obscure books in Amazon though they are on Amazon Kindle. They get drowned out in the Amazon river. Sometimes, alas, you have to go to pdfs or physical copies because even Kindle doesn't have it.
If you don't like reading oline,
Seawolf Press has lovely paperbacks of popular classics, and Thriftbooks has some beautiful hardbacks for reasonable prices (I have one of Tristram Shandy and one of David Copperfield).