Under the Net
I'm currently reading Iris Murdoch's Under the Net (1954). There is a great sequence about the problem of language: 'The whole language is a machine for making falsehoods'. Murdoch's novel combines sharp wit with a disarmingly lowkey but dextrous prose style ('Astonishingly soon the daylight came, like a diffused mist') and there is a constant philosophical inquiry underlying the entire project. She's a perfect forgotten classic, well known but unread.