Add the site to your home screen: it opens like an app, full screen, and pages you have read stay available offline. Nothing to download from a store.
iPhone / iPad (Safari)
Tap Share at the bottom of Safari, then Add to Home Screen and Add.
Android (Chrome)
Open the Chrome ⋮ menu, then Install app (or Add to Home screen).
Computer (Chrome, Edge)
Click the Install icon on the right of the address bar, or menu ⋮ > Install. Firefox and Safari on desktop do not offer installation: you can bookmark the site.