Related: A command-line tool I wrote a while ago called Erudite that pulls articles from Instapaper or Pocket and converts them to an ebook format (uses Calibre as the conversion tool, all processing runs locally on your machine (aside from the calls to Instapaper or Pocket, of course)).

(It even has Hacker News integration that includes URLs for corresponding posts!)

https://github.com/evmcl/erudite