Ok, this gets complicated. Walter Hooper's C.S. Lewis: A Companion & Guide has the answer.
Lewis sold a bunch when he retired from Magdalene College, Cambridge.
At his death there were 3000 volumes left, which he left to his brother, Warnie.
Warnie, per Jack Lewis' instrutions, allowed allowed Jack's closest friends to take what they wanted, about 100 all together went to them.
Warnine sold the rest to B.H. Blackwell Booksellers, who in turn sold 200 to Walter Hooper, and 2710 to , Banbury, a campus of the Fairleigh Dickinson University of New Jersey.
Hooper gave 176 of his books to the University of North Carolina at Chapel Hill, and a few others to the Bodleian Library in Oxford.
So, if you want to see his libary, your best best is Wroxton, next UNC at Chapel Hill.
Hope this helps.
Selah,
Sven
