I find the Brahms Rhapsodies really interesting; there's a lot hidden in the score and it takes a bit of time to digest and interpret these pieces. I have studied the first one in depth with my teacher, and we focused on orchestration in particular in order to bring out character and voices. The piece is not written in a pure, 'pianistic' style - rather, it is quite easy to imagine an orchestra performing it with different instruments playing the various motifs. As an example, start thinking about how a cello would perform bars 22-27. For me, this way of thinking about the score has allowed the piece to breath and come alive.