You git clone the repo (assuming you have git installed). You then have to npm install (assuming you have node installed). You then have to npm install sharp. But before sharp can work, you have to npm install node-gyp. But in before that can work, you have to make sure you're using a specific version of Python, specific versions of Visual Studio (2010 and 2015 both seem to fail), an SDK, and then run some console commands to set the WindowsSDKDir.
After you spend 30 minutes downloading and uninstalling and re-installing different version of Visual Studio and SDKs and sorting out other error messages, you're finally back to trying to install sharp. You install sharp, but wait, then you need to download this zip file and change your environment variables and PATH variables, which you have to Google to remember how to do each time because it's done so rarely.
This is obviously all feasible and to an experienced developer not intimidating, but for someone who's on a Windows machine and new to node, it doesn't seem like simply getting a package running should be this difficult in 2015. The demo is broken and I wanted to check it out, but it's just not worth the effort.