As we gear up for Narnia-mania, I was not surprised to see in The New Yorker,
PRISONER OF NARNIA by ADAM GOPNIK (How C. S. Lewis escaped.). Here are some choice quotes:

It seemed like an odd kind of conversion to other people then, and it
still does. It is perfectly possible, after all, to have a rich
romantic and imaginative view of existence—to believe that the world is
not exhausted by our physical descriptions of it, that the stories we
make up about the world are an important part of the life of that
world—without becoming an Anglican. In fact, it seems much easier to
believe in the power of the Romantic numinous if you do not take a
controversial incident in Jewish religious history as the pivot point
of all existence, and a still more controversial one in British royal
history as the pivot point of your daily practice. Converted to faith
as the means of joy, however, Lewis never stops to ask very hard why
this faith rather than some other. His favorite argument for the truth
of Christianity is that either Jesus had to be crazy to say the things
he did or what he said must be true, and since he doesn’t sound like
someone who is crazy, he must be right. (He liked this argument so much
that he repeats it in allegorical form in the Narnia books; either Lucy
is lying about Narnia, or mad, or she must have seen what she claimed
to see.) Lewis insists that the Anglican creed isn’t one spiritual path
among others but the single cosmic truth that extends from the farthest
reach of the universe to the house next door. He is never troubled by
the funny coincidence that this one staggering cosmic truth also
happens to be the established religion of his own tribe, supported by
every institution of the state, and reinforced by the university he
works in, the “God-fearing and God-sustaining University of Oxford,” as
Gladstone called it. But perhaps his leap from myth to Christian faith
wasn’t a leap at all, more of a standing hop in place. Many of the
elements that make Christianity numinous for Lewis are the pagan
mythological elements that it long ago absorbed from its pre-Christian
sources. His Christianity is local, English and Irish and Northern.
Even Roman Catholicism remained alien to him, a fact that Tolkien much
resented.

[....]

Yet a central point of the Gospel story is that Jesus is not the lion
of the faith but the lamb of God, while his other symbolic animal is,
specifically, the lowly and bedraggled donkey. The moral force of the
Christian story is that the lions are all on the other side. If we had,
say, a donkey, a seemingly uninspiring animal from an obscure corner of
Narnia, raised as an uncouth and low-caste beast of burden, rallying
the mice and rats and weasels and vultures and all the other unclean
animals, and then being killed by the lions in as humiliating a manner
as possible—a donkey who reëmerges, to the shock even of his disciples
and devotees, as the king of all creation—now, that
would be a Christian allegory. A powerful lion, starting life at the
top of the food chain, adored by all his subjects and filled with
temporal power, killed by a despised evil witch for his power and then
reborn to rule, is a Mithraic, not a Christian, myth.

[....]

It is tempting to say that Lewis, in the dramatic retellings of this
story, becomes hostage to another kind of cult, the American cult of
salvation through love and sex and the warmth of parenting. (She had
two kids for him to help take care of.) Yet this is exactly what seems
to have happened. Lewis, to the dismay of his friends, went from being
a private prig and common-room hearty to being a mensch—a C. of E.
mensch, but a mensch. When Joy died, of bone cancer, a few years later,
he was abject with sadness, and it produced “A Grief Portrayed,” one of
the finest books written about mourning. Lewis, without abandoning his
God, begins to treat him as something other than a dispenser of vacuous
bromides. “Can a mortal ask questions which God finds unanswerable?
Quite easily, I should think,” he wrote, and his faith becomes less
joblike and more Job-like: questioning, unsure—a dangerous quest rather
than a querulous dogma. Lewis ended up in a state of uncertain personal
faith that seems to the unbeliever comfortingly like doubt.