I sure like Lewis more than I like Rowan Williams.....,
I'm not sure I trust Rowan Williams to say anything useful about Lewis.
Far better to cut to the chase and just read Lewis in the original. As Lewis himself said,
There is a strange idea abroad that in every subject the ancient books should be read only by the professionals, and that the amateur should content himself with the modern books. Thus I have found as a tutor in English Literature that if the average student wants to find out something about Platonism, the very last thing he thinks of doing is to take a translation of Plato off the library shelf and read the Symposium. He would rather read some dreary modern book ten times as long, all about "isms" and influences and only once in twelve pages telling him what Plato actually said. The error is rather an amiable one, for it springs from humility. The student is half afraid to meet one of the great philosophers face to face. He feels himself inadequate and thinks he will not understand him. But if he only knew, the great man, just because of his greatness, is much more intelligible than his modern commentator. The simplest student will be able to understand, if not all, yet a very great deal of what Plato said; but hardly anyone can understand some modern books on Platonism. It has always therefore been one of my main endeavours as a teacher to persuade the young that firsthand knowledge is not only more worth acquiring than secondhand knowledge, but is usually much easier and more delightful to acquire.
- "On the reading of old books" - preface to Athanasius, "On the Incarnation"