Not very hard, but time consuming... then again what layout isn't now-a-days. The only part I couldn't reproduce myself in a couple hours would be the drop down archives/categories/search div, but that's because I don't know javascript/ajax worth a dime - however it looks like they're just using mootools to do it, so it's probably pretty easy with that library to recreate the effect. I'm sure there's tutorials on it all over the web. If you're ever curious about how somebody did something, check the source, and download a copy of their style sheet to dissect it.

It should be even easier to reproduce, actually, considering it's based off the hemingway theme that you could just download and use yourself.
-m