As large as C. S. Lewis looms in today's intellectual landscape, and for all the different ways he manages to find a readership, whether as a literary critic, a Christian apologist, or fantasy novelist, it is somewhat surprising that we do not yet have a truly first rate biography. Until that volume comes along, this affectionate biography/memoir by Lewis's student/friend George Sayer is the best that we have.
The great problem in C. S. Lewis scholarship at the moment is that the bulk of the books dealing with his life tend to be overwhelmingly pious and respectful (the St. Jack bios) or intent on tearing holes in that portrait (A. N. Wilson). What we really need is a first rate biography that manages to capture the magic and appeal of Lewis's personality, explains his ongoing intellectual and imaginative appeal, and yet does not willfully overlook the man's flaws. Sayer captures the personality marvelously, gives some hints as to his intellectual appeal, but presents a fairly sanitized version of Lewis's life. No doubt this is out of respect and affection, but Lewis doesn't emerge as a warm flesh and blood human being. For instance, while alluding to his relationship with Mrs. Moore, Sayer assumes a position of agnosticism as to its nature. It is an important if disturbing chapter in Lewis's life, because it potentially reveals a great deal about his personality.
One thing that does emerge in Sayer's biography is the closed reserve that Lewis seems to have carried with him all his life. On the one hand, Lewis seems to have been a very accomodating, kind, and helpful soul, and yet, he is hard to get to know. One gets to know his thoughts, and yet never gets to know the man who thinks them. One can read both SURPRISED BY JOY and A GRIEF OBSERVED, and come away from them not having a strong sense of how Lewis felt about things, about the predomenant emotions in his life. Sayer doesn't completely dispell this emotional reserve that Lewis projects, but he probably gets as close as anyone has.
Still, I don't believe this is the biography we are waiting for. It will do until the definitive one comes along. My recommendation for those wanting to know about Lewis's life is to read this one in conjunction with A. N. Wilson's. In the latter Wilson far too gleefully deconstructs the carefully constructed portrait of Lewis that some of his more somber admirers have constructed. I value the Wilson as a corrective, but one will not get much of a sense of why Lewis was such an attractive individual for so many, both in his books and in real life. For that, you will need to look to this excellent book.