Could you recommend authors who are/were similar to C.S. Lewis or maybe some Muslim poets whose poems are pretty decent and not too engaged in worldly love affairs. Thank You.
Why not C. S. Lewis himself? His 4000-page Collected Letters is wonderful. He also has about 20 books, all of which are worth reading. The only other authors I know who would be like him are Tolkien (they were actually good friends) and George MacDonald (a writer whom Lewis admired greatly). If you read Lewis’s Collected Letters, you will see hundreds of other books and writers mentioned in it that may be worth checking out.
I don’t know any Muslim writers who reach their level of sophistication and understanding, except for possibly Said Nursi.
As for poetry, you can check out this page on Amazon.com which has translations of many Persian mystical poets. Note that all the great classical Persian poets were Sunni (if you are worried about theological differences).