View-mode makes for great read-only reading

The built-in view-mode turns the current buffer into a read-only pager, with SPACE and DEL to scroll up and down by page. This is a nice way to comfortably read files. Simply toggle on or off with M-x view-mode (or use e to exit view-mode). You can also tell Emacs to always open read-only files in view-mode with:

(setq view-read-only t)