I assume you mean only the prescribed texts but not any of your related material? It's not recommended, and I don't want to instil false hope but yes it is possible. I only read 3/5 of my core texts and one of my related texts and I managed a band 6. Just keep in mind that you have to make up for what you would have if you read the books, by making sure you have strong quotes, plenty of techniques to back them up and very certain insight into how the quotes/techniques fit into your essay or theme.