How is this even legal in the US? - in the UK you can only sue the producer of violating product and not the distributer, and even threatening a distributer without having first won a court case against the producer is illegal (to stop companies strong-arming distributers with patent threats regardless of the validity of the patents which the distributer can't reasonably expected to be knowledgable about).

It seems in this case the lawsuit is against functionality in Android and B&N are merely the distributer.