Possession
By A.S. Byatt

This is one of those books where the first 100 pages are a little tough but then it goes like a freight train. It's a mystery, told in alternating stories: The first follows two academics who are trying to discover whether a pair of 19th-century poets had a love affair; the second is what actually happened between the poets. As the modern-day scholars look through letters and historical documents, you see how the poets' relationship affects them. The book tackles questions like "Are people really all that different from era to era? How much do we really know of what came before—even if we have letters and other remnants of the past? How do you weigh the importance of what people say with how they say it? What is art used for?" I love books that force me to move a little outside my comfort zone, and this one was deeply satisfying.