Everybody has heard of black holes, they're up there with the Big Bang and E=mc2 in the public physics consciousness. They've gone from a rather odd solution to some of Einstein's equations, to science fiction staple, to conventional astrophysics in around a century, and nobody has ever seen one.
There's certainly a lot of circumstantial evidence though, notably a lot of extremely high energy events a (thankfully) very long way away, and a very, very dense object at the centre of our own Milky Way called Sagittarius A* (pronounced "A-star"). Current theories of physics also suggest we may find oddities like miniature black holes created in the moments after the Big Bang; stranger and more speculative still, our entire Universe looks in many ways like the view from the inside of a black hole's event horizon.
Mitchell Begelman, Professor of astrophysical and planetary sciences at the University of Colorado, and Martin Rees, the UK Astronomer Royal and master of Trinity College Cambridge certainly have a pedigree when it comes to these strange objects, and they've written a lucid and very beautiful account of the current research. This falls into one of my favourite areas of science books - it's either an extraordinarily well presented undergraduate text, or a popular science book that goes that bit further, purposefully ignoring the "no equations" dictum. There are equations, there are graphs. And diagrams, photos, diagrams and graphs overlaid on photos and so on and so forth. They're all glossy full colour and very pretty for the most part, and it's a far better book for it. The diagram-on-photo of stars frantically orbiting something very massive and very small at the centre of out galaxy is the first thing I've seen that actually convinces me black holes exist outside of theory. The prose is flowing, informative and packed with interesting side notes and magazine style sidebars and sub-articles highlighting important concepts like spectroscopy or hyperbolic geometry.
Three hundred pages of cutting edge, high level astrophysical research rewritten for people who understand the odd graph and like pretty pictures - fantastic.
Incidentally, go and see Martin Rees give a lecture at some point if you can, he's a very interesting man indeed.
Gravity's Fatal Attraction
Mitchell Begelman & Martin Rees
Cambridge University Press