You should have a good working knowledge of computer networks and vulnerability scanning so you can understand the terminologies and methodologies used in this book.
In order to follow the recipes, you will need to be running Windows or Kali Linux, and will require Metasploitable 2 by Rapid7 with the latest versions of Nmap and Nessus. For some of the recipes, such as those to do with configuration audits, you will need to have a Nessus professional license.