Variations on a theme:
Truth is always strange; stranger than fiction
- Lord Byron
Truth is always stranger than fiction, but it is because fiction is obliged to stick to possibilities and truth isn't.
- Mark Twain
Truth must necessarily be stranger than fiction, for fiction is the creation of the human mind and therefore congenial to it.
- G.K. Chesterton
Truth is stranger than fiction; fiction has to make sense.
- Leo Rosten, also, Tom Clancy