The Staff Rules and Regulations (R I 13.04) require the prior written authorisation of the Director-General for members of personnel making any communication outside the Organisation in which they identify themselves as such or make references to CERN’s functioning or activities.
In addition, you should remember that the novel should be written outside your working hours and its content should be compatible with your obligations as a CERN contributor, in particular your obligations of reserve, tact, discretion and confidentiality. You should advise your Department Head who is best placed to assess this compatibility.