Black holes are well known objects, but their study using general relativity requires some difficult mathematics. In Black Holes and Time Warps: Einstein's outrageous legacy
Kip Thorne manages to put over some highly theoretical notions without needing any mathematical details - the excellent drawings by Matt Zimet are a great help. Although it is a large book it has a very readable style. It might also serve as a source book for further study, as its biographical details of the main people in the field give a starting point to investigate their work. Its a valuable addition to the bookshelf of anyone who is interested in the development of modern ideas about space and time.
The book describes Einstein's development of general relativity and how the possibility of black holes arose with the work of Schwarzchild. This leads on to the study of compact objects by Chandrasekhar and Zwicky, which was strongly resisted by Eddington and Einstein. Thorne also looks at how the Cold War interfered with the study of General relativity, and how a new 'golden age' of black hole research started in the 1960's with the acceptance that they weren't just frozen stars. Later chapters deal with Hawking radiation, gravitational waves (Thorne's speciality) and the possibility of time travel using wormholes.