Unless the author publishes a detailed paper on what they wanted to communicate in their work, you never really "get" a book.

You only get your subjective perception of the book. Now, I'm not saying that the author can't communicate a message to the reader, but not all authors try to do that.

Some authors just want to write a a bunch of characters and events and stories and don't really care if the reader understands the point or meaning. Some works of art don't have a true meaning.

Just because a book doesn't have an understandable meaning, however, doesn't mean that it's bad or unenjoyable. Goodness and enjoyability are just subjective to the reader.