There's a print-friendly stylesheet, so you can easily print each article. You could probably automated this using the RSS feed.

But I'm not sure I'd want a printable book. The articles are each standalone so you'd need to figure out some logical sequence. Plus once you print it you can't make improvements to existing articles.

Around the time I turned 11 or so, my dad bought be a "how stuff works" book; definitely written to a "newspaper" reading level. It was paperback, not a lot of pictures, and generally held my interest. I think it targeted older teenagers or adults.

What surprised me was halfway through there was a section on how hash is made!