Game Over: Kasparov and the Machine is a decent enough documentary on the subject. The coverage does kind of imply that Kasparov was grasping at straws a bit. Like a typical World championship match there was a lot of behind the scenes tactics going on from both sides.
My feeling is that you only have to look at the ascent of Anand and other chess players who rely heavily on computers in their training and analysis to realise that, at the time of this match, there was a paradigm shift from human to computer as the dominant chess player.
Addendum:
There's a interesting tidbit in Nate Silver's “The Signal and the Noise: Why So Many Predictions Fail—But Some Don’t.” In it he describes an interview with one of the engineers who worked on Deep Blue:
Nevertheless, there were some bugs in Deep Blue’s inventory: not many,
but a few. Toward the end of my interview with him, [Murray] Campbell
somewhat mischievously referred to an incident that had occurred
toward the end of the first game in their 1997 match with Kasparov. “A
bug occurred in the game and it may have made Kasparov misunderstand
the capabilities of Deep Blue,” Campbell told me. “He didn’t come up
with the theory that the move it played was a bug.” The bug had arisen
on the forty-fourth move of their first game against Kasparov; unable
to select a move, the program had defaulted to a last-resort fail-safe
in which it picked a play completely at random. The bug had been
inconsequential, coming late in the game in a position that had
already been lost; Campbell and team repaired it the next day. “We had
seen it once before, in a test game played earlier in 1997, and
thought that it was fixed,” he told me. “Unfortunately there was one
case that we had missed.” In fact, the bug was anything but
unfortunate for Deep Blue: it was likely what allowed the computer to
beat Kasparov. In the popular recounting of Kasparov’s match against
Deep Blue, it was the second game in which his problems
originated—when he had made the almost unprecedented error of
forfeiting a position that he could probably have drawn. But what had
inspired Kasparov to commit this mistake? His anxiety over Deep Blue’s
forty-fourth move in the first game—the move in which the computer had
moved its rook for no apparent purpose. Kasparov had concluded that
the counterintuitive play must be a sign of superior intelligence. He
had never considered that it was simply a bug.
