Now despite the fact that this book is mainly philosophy, Dawkins is not a philosopher (he’s a biologist). Even taking this into account, however, much of the philosophy he purveys is at best jejune. You might say that some of his forays into philosophy are at best sophomoric, but that would be unfair to sophomores; the fact is (grade inflation aside) many of his arguments would receive a failing grade in a sophomore philosophy class. This, combined with the arrogant, smarter-than-thou (‘thou’ being believers in God) tone of the book can be annoying. I shall put irritation aside, however and do my best to take Dawkins’ main argument seriously.
Dawkins' book makes you wonder about all the times we've heard that science should be completely set apart from other disciplines. If we really took this advice and drew such lines dividing the disciplines, then why is Dawkins (a scientist) writing a philosophy book? That aside, the book made many poor arguments and, despite its best-selling status, is only worth reading to understand Dawkins' thought process.
As for Alvin Plantinga, he is highly regarded as one of the top philosophers history has even seen. His areas of focus are epistemology and philosophy of religion and it has been said of him that he is the greatest philosopher of religion since Gottfried Leibniz and possibly even since Thomas Aquinas.