Malen'kaia kniga o chernykh dyrakh - Gabser S.,Preto

Despite the complexity of the topic, Princeton University professor Stephen Gabser offers a capacious, accessible and entertaining introduction to this one of the most talked about areas of physics today. Black holes are real objects, not just a thought experiment! Black holes are extremely convenient from the point of view of theory, as mathematically they are much simpler than most astrophysical objects, such as stars. Oddities begin when it turns out that black holes are not really so black.
What is really inside them? How can you imagine falling into a black hole? Or maybe we're already falling into it and just don't know about it yet?