It's basically just a showcase for hops. They have higher alcohol and hop bittering and aroma than a regular IPA. But like jerryboy said, there is a lot of room for creativity in the style. Some, like DFH 90 minute and Great Divide Titan have a pretty strong malt backbone, while others like Odell Myrcenary and Stone Ruination are a punch of straight hops to the face. If you can find a somewhat widely available commercial example that you really like, you can probably find a clone recipe of it somewhere on the internet and either brew that as-is or make some slight modifications to fit your tastes.