In a preface to The Pilgrim’s Regress that he wrote in 1943 (ten years after the book was first published), Lewis said that he now found that the book was “needlessly obscure” and “uncharitable.” This isn’t his best book by a long shot. It’s interesting, both as insight on Lewis himself and as a complicated allegory (and, yes, it’s really allegory, unlike the Narnia books which are incorrectly referred to as allegory), but it’s hard to say if you’ll really enjoy it.