The book dives deep into the tons of fossil evidence discovered throughout the earth, which have been meticulously calculated to be in the right order. For example, a flying creature has been discovered to live only after the evolution of wings, not before. Not once has there been any fossil records discovered from the wrong time. If you find one, evolution will be debunked -- I'm not holding my breath.
But here's the kicker: even if there were no fossil records, evolution would still stay ground on the basis of all the other scientific evidences. That we have the arsenal of fossils available to us is a bonus. It further reinforces evolution. Evolution is in line with the myriad forms of life that exist on the planet. It explains why life is imperfect (it's still evolving). It explains why creatures have different abilities depending on their habitat. It does not lead to paradoxes. Compare this with the creationist argument of an intelligent designer (God) where even if you are somehow able to explain who created God, you still have all the explaining ahead of you. Why is there misery? Why is there sorrow (unless of course if you agree that God is a sadist)? Why is that some creatures have acute vision while others are practically blind? Why do we have redundant body parts (appendix, tail bone, ..)? Why do we have body parts which would have been much efficiently designed if an "intelligent" designer was devising them? Evolution answers all of these.
Not that I ever doubted evolution, but I never realized how profound it was in shaping life. Nature cares about only one thing: the survival of the fittest. Period. It doesn't matter if it leads to widespread agony, plague or earth quake. Nature is not interested. At every point the genes undergo random mutation, and nature selectively votes in favor of the ones that have a high chance of survival, thereby carrying forward the genetic code.
The book ends beautifully with: We are surrounded by endless forms, most beautiful and most wonderful, and it is no accident, but the direct consequence of evolution by non-random natural selection -- the only game in town, the greatest show on earth.
There really is grandeur in this view of life.