I noticed that iTunes preview allows you to crawl and scrape pages via the http://
protocol. However, many of the links are trying to be opened in iTunes rather than the browser. For example, when you go to the iBooks page, it immediately tries opening a url with an itms://
protocol.
Are there any other methods of crawling the App Store or is this the only way?
Can the itms://
protocol links themselves be crawled somehow?
I would have a decent look at the iTunes Search API and the iTunes Enterprise Partner API
You might get most/all of the information you need in a nice JSON file format.
If you can't get the information you need with the API, I would be interested what it is :)