Excellent post @chbarist, it is interesting the evolution that each reader develops from the beginning, from the first book. If we made a list from the first book to the last, we would discover the changes in our tastes, the way of thinking and seeing the world. Reading speed also increases over time but there are books that should definitely be read slowly.
Another interesting thing is that what we discover in a book will depend on our level of knowledge and awareness, we can read the same book 5 years later and perceive things that we could not before.