The main difference between brown IPA and American IPA lies in the blend of malts and the resulting colour of the beer. Brown IPA is darker than American IPA but lighter than black IPA.
In addition to hop bitterness, flavours of caramel, chocolate, and/or toffee may be present. Brown IPA is slightly more flavourful and maltier than American IPA but is not as sweet or heavy as many other dark beers.
Brown IPA is yet another experiment in the world of IPAs. It was born from blending several malts together to achieve the desired colour and taste profile.
Brown IPA has never achieved widespread success and is quite a niche beer style.