I have posted several times on R' Shlomo Carlebach, one of the great pioneers of true Jewish music. This coming week will be the Yahrtzeit, consequently a new post is in order.
Recently, one of RSC's Talmidim has published some of his Chiddushim. I have not seen the Sefer, so I can't comment on it, although based on past experience I would imagine it will probably be of the Chassidic genre.
The best book I ever read about RSC is Holy Brother, by Yitti Halberstam. The stories are remarkable. It is in my opinion, one of the best books written in English for the Jewish public. What I find notable about the book, is that there are so many stories which portray his innate drive to help the unfortunate. It was typical of him to give away all his money, and when he passed away, it is said that all he had left were his daughters and 20,000 Seforim.
For some vintage RSC, see this.