The Painted Veil by William Somerset Maugham

Kitty did not know whether it was by chance or by design that she never found herself for a moment alone with Charlie. His tact was exquisite. He remained kindly, sympathetic, pleasant and amiable. No one could have guessed that they had ever been more than acquaintances. But one afternoon when she was lying on a sofa outside her room reading he passed along the verandah and stopped.

‘What is that you're reading?' he asked.