Following on from Norton is a more detailed guide to the objects of the night sky. There are countless books out there in all shapes and sizes that provide a detailed field guide to the constelaltions and the objects you can find by naked-eye, binocular and telescope.
Arguably the most autoritative is this offering by Collins publishers. It is edited by Ian Ridpath, perhaps the foremost expertise in this area, and in its latest version contains many updated images of deep sky objects as well as useful advice on selectign and buying astronomical instruments.
In addition, as an acknowledgement of the changing times many of the resources are also available for download.
