"Reason and Belief" is an extraordinarily thorough, and painstakingly fair, critique of Christianity in both its Catholic and Protestant forms, grounded in an exhaustive knowledge of his subject.
Perhaps surprisingly, anyone genuinely desiring a clear understanding of Christian doctrine would do well to go here to find it, as many aspects of Christianity are today very poorly understood even by Christians.
Equally important, however, is Blanshard's answer to this question: if many today cannot accept Christianity as the foundation of their values, where do they go from there?
The attempt by philosophers like Jean-Paul Sartre to answer this question left many dissatisfied. Blanshard's answer is far more satisfying, complete, and illuminating.