HTTrack is a free software (GPL) offline browser utility, allowing you to download (copy) a website from the Internet to a local directory, building recursively all directories, getting html, images, and other files from the server to your device.

HTTrack arranges the original site's relative link-structure. Simply open a page of the "mirrored" website in your browser, and you can browse the site from link to link, as if you were viewing it online.
HTTrack can also update an existing mirrored site, and resume interrupted downloads.

(This is the Android version of the popular Website Copier.)

Android 6 & 7 fixes (crashes at startup and/or during browse), SDcard is now selected by Additional Android 6 (Marshmallow) and 7 (Nougat) fixes related to crash at startup and/or issues accessing downloaded websites (crashes when asking to browse or see the documentation), and update to the latest