The best thing about ScrapBook+ is that it can follow hyperlinks and capture those web pages as well. Rarely, you come across a web page that doesn't have any hyperlinks. In fact, that's the beauty of the world wide web. Every web site or page links to other websites which links further to more websites, thereby enabling a user to browse through these interconnected pages and discover more and more new sites. There is no dead end. However, when you save a page and later open it to read, it's a dead end. Often you realize that you need to open these hyperlinks and therefore have to go online again, which defeats the very purpose of saving a page.
But with ScrapBook+ you can save a page and all the linked pages and even all pages linked by the linked pages. In fact, you can go on and on. But for all practical purposes, a link depth of 1 is sufficient, which means it will only save the pages that the original page links to. So when you capture a page with link-depth 1, all the hyperlinks on the page works even when offline.
Now sometimes, you might want to do the opposite. Say, you want to save only a part of the page. Then instead of saving the whole page you can select only the part you want to save and click "Capture selection". Again, instead of saving you can bookmark a part of the page, so that when you open that bookmark you will be presented with only the part of the page you captured. Cool isn't it?
ScrapBook+ is an experimental addon and requires you to login to install. Alternatively, you can use the direct install link.