I've just tried Readeck and it doesn't save a good quality copy of the pages using the Firefox extension. SingleFile and WebScrapBook do a much better job.

I prefer WebScrapBook because it saves all the assets as files under the original names in a directory rather than a zip file. This means that I can use other tools such as find, grep, and file managers like Nemo to search the archive without needing to rely on the application that saved the page.