If the author of this book is one of the credentialed scientists you speak of, then I'm afraid you've been swindled, he doesn't appear to understand the basics of natural selection.
If this review accurately reflects the content of the book (which, by the way, has a UFO on the front cover???) it demonstrates the author's lack of understanding. Yes, people are born with many deletarious mutations, and like he says most are insignificant. But the first obvious mistake is his use of the term "fitness", the fitness of an individual isn't determined by how many mutations they have, it is determined by how long they survive and how many offspring they produce. It doesn't matter if a person is riddled with bad point mutations, if they survive and reproduce, they are fit in evolutionary terms.
Secondly, mutations don't simply accumulate over generations like he's proposing, within a population there will be enough differing alleles to diluate out most deletarious mutations. For a mutation to become fixed into the population, the individual must have enough children to significantly alter the genetic dynamics of that population, overwhelming the influence of competing alleles. And if he has the fitness to produce that many offspring, it means his mutation is not a hindrance to his survivial in his current habitat. And that is key, the fitness of a certain individual is determined not on his genetic structure alone, but in the ways in which that genotype allows him to interact with his environment.
You don't need to believe in evolution, but if you want to
understand it you can't rely on those pushing a Christian agenda, you need to read books by those who work in the field, and that doesn't necessarily mean Richard Dawkins. Just go to the library or pick up a cheap copy online of Evolution: An Introduction by Sterns and Hoekstra.
Amazon.com: Evolution: An Introduction (9780198549680): Stephen C. Stearns, Rolf F. Hoekstra: Books