C. S. Lewis
I've been reading books by C. S. Lewis since I was about 11 or 12 I think, starting with 'The Lion, the Witch and the Wardrobe' in a Dutch translation, since then I've added a whole lot more to my Lewis list, some in Dutch then later re-read in English, others in English only. This is not the place to say which book is my favorite, Lewis wrote in so many different styles and genres it's hard to pick just one 'best of'. At different times I've enjoyed different books, sometimes the science fiction trilogy was a close companion, some days 'the problem of pain'.
The ones I can highly recommend are, the Narnia chronicles, 'The Screwtape Letters', 'Mere Christianity', 'The Four Loves', the Space Trilogy (esp "That Hideous Strength"), 'Till we have faces' and 'The Great Divorce'.
Other books I have read by Lewis include:
The Pilgrims Regress (recommended)
Fern Seed and Elephants
The Problem of Pain
The Abolition of Man
God in the Dock
The Dark Tower and other stories
Letters to Malcom-Chiefly on prayer
Poems
Of This and Other Worlds
Highly recommended
Interesting
Wish List