Charles Rosen discusses a number of Brahmss imitations of Beethoven in chapter 9 of his Critical Entertainments: Music Old and New (2000; Cambridge, MA: Harvard University Press, ISBN 0-674-17730-4).Brahms by Malcolm MacDonald is a biography and discussion of virtually everything Brahms composed, along with chapters examining his position in Romantic music, his devotion to Early Music, and his influence on later composers. (Dent Master Musicians series, 1990; 2nd edition Oxford, 2001, ISBN 0-19-816484-X)