How vocal the book is in my head depends on how distinctive the narrative voice is. It's absolutely IMPOSSIBLE to read the Lonely Londoners, say, without hearing voices. Something more recent that I found had a very distinctive voice is Notes on a Scandal - Zoe Heller. Obv, they're both first-person narratives, and that makes it a lot easier to 'hear the voices' because you're immersed right in it.