The answer to the title's question is, unsurprisingly, "yes", but the argument supporting the answer is certainly not trivial. Wilson arrives at the answer only after careful analysis, e.g. by making a distinction between altruism in action and altruism in thought. The book is based on the notion of group selection in evolution, a concept recently rehabilitated by, among others, the author himself. Group selection, or more generally, multi-level selection, can occur under fairly well-defined circumstances, overriding or modifying "ordinary" individual selection. Rather than disproving the selfish gene theory, Wilson clarifies why and how that theory is not and cannot be the whole answer.
Wilson also ventures into the arena of politics and philosophy, which is a dangerous thing for biologists, and evolutionists in particular, to do. But he pulls it off admirably. The discussion centers around Elinor Ostrom's theory of how the tragedy of the commons can be avoided (a prime example of altruism in action), and the connection of this concept to evolutionary mechanisms is explored. An interesting and provocative observation is that altruism is actually a modern concept, and does not figure in the major religions, at least not under the definition used by Wilson.