i'm looking for a hard sf book that deals with black holes, in any context, whether it is exploring one or studying one etc.

You may want to give David Brin's "Earth" a try. Though it has been a long time since I read this, I remember that the story-line involved the consequences of a small black hole falling into the center of the Earth. While this is a work of science fiction, Brin tends to use real science and create situations that seem to be plausible. I recall that the book takes place several decades into the future, hence Brin also tries to tackle issues such as environmental degradation, overpopulation, etc.