The important point is covered in a paper by Erwin et al. (2011). It shows that the main animal groups probably split gradually over a period of tens of millions of years before the "explosion" became visible in the fossil record [see The Cambrian Conundrum: Fossils vs Genes]. The authors show that the molecular data indicates an earlier divergence and trace fossils are consistent with that data.
The other book is about to be published. It's called Darwin's Doubt: The Explosive Origin of Animal Life and the Case for Intelligent Design and the author is an expert paleontologist and evolutionary biologist named Stephen Meyer.
It certainly sounds exciting if you read the announcement on Evolution News & Views (sic) [Coming in June, a Game-Changing New Book: Darwin's Doubt, by Stephen Meyer].
We've been keeping something from you, dear readers, but now it can be told. The evolution debate is about to undergo a paradigm shift....It would not be fair to criticize Meyer's book before we get a chance to read it. It will be fun to see how the science compares with that in the book by Erwin and Valentine. I'm really looking forward to reading about the Intelligent Design Theory that explains all of the scientific data. I'm especially curious about why the designer did the deed 530 million years ago and why everything since then looks so much like evolution. I'm sure that's going to be covered. We can be practically certain that a paradigm-shifting book like this isn't just going to be several hundred pages of evolution bashing.
Here is a sweeping account, stunningly illustrated with gorgeous color photos, of the frontiers of the scientific critique of Darwinism and the case for ID. Exacting and thorough, yet remarkably accessible to the thoughtful lay reader, Darwin's Doubt introduces us to the challenges to Darwinism based on the study of combinatorial inflation, protein science, population genetics, developmental biology, epigenetic information, and more.
Meyer explains how post-Darwinian alternatives and adaptions of Darwin's theory -- including self-organizational models, evo-devo, neutral or nonadaptive evolution, natural genetic engineering, and others -- fall short as well. He demonstrates that the weaknesses of orthodox evolutionary theory, when flipped over head-to-foot, are precisely the positive indications that point most persuasively to intelligent design.
Evolutionary biologists studying gene regulatory networks and fossil discontinuity, among other fields, have come tantalizingly close to reaching this conclusion themselves.
The Cambrian event, fundamentally, represents an information explosion, the first but not the last in the history of life. As no book has done before, Darwin's Doubt spells out the implications of this fact. Dr. Meyer stands on the verge of turning the evolution debate in an entirely new direction, compelling critics of the theory of intelligent design, at last, to respond substantively and in detail. The book will be a game-changer, for science and culture alike.
Erwin, D.H., Laflamme, M., Tweedt, S.M., Sperling, E.A., Pisani, D., and Peterson, K.J. (2011) The Cambrian conundrum: early divergence and later ecological success in the early history of animals. Science 334:1091-1097. [PubMed] [doi: 10.1126/science.1206375]