Practically anything by George Eliot. Her mind is incredibly powerful and analytical.
The best one by her I've read so far is Middlemarch. It's not an easy read - long and convoluted, with dozens of characters and dense, sometimes endless paragraphs. In a way, it's a historical novel, because she is setting it some forty years in the past (around 1830) from when she wrote it (1871), and she tracks many real events that were unfolding at the time of the action in the story line.
Eliot really lights up the inside of her characters. She doesn't just describe actions. She shows the wheels turning inside the heads of the characters, showing why they do what they do. There is often a little philosophical paragraph set in the action that illuminates some principle of human behavior.
Eliot herself is a fascinating figure. She was Mary Ann Evans. She adopted the pen name of George Eliot because she refused to be pigeonholed as a "female novelist" at a time in England when female writers were treated with condescension. She lived a remarkably unconventional life for the time, consorting with all manner of freethinkers, scientists, radicals, and progressive intellectuals.
