HTTrack Website Copier is always my favourite. Internet is not always available. Download a website, especially articles, for offline reading is always a good solution. HTTrack is the best. Previously I used GUI, but in Linux, command-line is a better method.
On the other hand, Android e-book reader I used most is FBReader. It supports multiple e-book format, especially EPUB. FBReader is easy to use, and there is night reading mode. Furthermore, it is open source and available in multiple platforms.
The best e-book management software I know is Calibre. The best feature is e-book conversion which supports various e-book format.
However, I have a problem with the downloaded website using HTTrack. The offline website is converted to EPUB format, which can be read by FBReader. Yet, because of the EPUB is a ZIP compressed file, opening the EPUB file requires to decompress it and retrieve the content. Moreover, the offline website is around 50 megabytes and contains around 4,400 files. This causes using FBReader to open the e-book requires more than 1 minute. This is extremely annoyance.
At the end, I choose to use Calibre to convert the offline website to a large size TXT format e-book. Now, I can read the offline website contents as e-book in my phone.
P/S: I tried to use mobile web browser to read the website online, even using the Reader View mode from Firefox. But there are a lot of disadvantages. Firstly, Internet connection is required. Secondly, Firefox cannot remember until where you have read, and bookmarking does not solve the problem. Thirdly, you cannot adjust the background colour and the text colour as easy as in FBReader. Each app is developed in a very different purpose.