Pete Hadcock was the Assistant Principal Clarinetist of the Boston Symphony for years, and played in the section with Harold Wright. He was a great player and an excellent teacher. Pete also studied with Hasty at Eastman, and I had the opportunity to take lessons with him when I was a Tanglewood Fellow.
His book contains practical clarinet studies for the serious player. It includes orchestral studies from Bartok and Brahms to Stravinsky and Tchaikovsky with in-depth performance advice. There are also master classes on the Nielsen and Mozart concerti, chapters on intonation, articulation, reedworking, fingering, and much, much more. Probably the most comprehensive book available for the serious clarinetist.