If you’ve picked up a Raspberry Pi, and want to learn how to do more with it than just play old video games, Humble’s newest ebook bundle is a terrific deal. 14 how-to ebooks are split across three different price tiers, and you can download all of them DRM-free for as little as $15. Most of them focus on the Raspberry Pi, but there are a couple of Arduino books in there too for wannabe tinkerers.