He is perhaps most famous on the internet for his "overdubs," in which he arranges popular pieces from movies or famous orchestra compositions and plays every part himself, layering the tracks to form one large trombone ensemble. A majority of these projects can be heard at his soundcloud page.
Recently, Nova has taken a number of his overdub arrangements and taken them to the performance hall. I had the opportunity to attend the Southeast Trombone Symposium last summer, which featured James Nova as a member of the faculty. He brought a number of his arrangements with him for the professors choir. Here is one of those pieces, a medley from Superman movies.
Because he originally arranged these for himself, where only one part had to be recorded at a time, the difficulty of the individual parts is remarkably high.