David Sparks just published his latest Field Guide to the iBookstore, this one covering all things Markdown. I’ve several times professed my love for Markdown; it’s literally changed the way I write (plain text files FTW). If you write things for the Web and don’t use Markdown, you’re crazy. It’s super easy to understand and learn with some practice. I'm downloading my copy of David's book as I type this, and I'm excited to dig in. I'm sure to pick up a few new tricks.