I just published my first book, Migrating to ServiceNow Event Management. In it, I provide tips and recommendations for migrating from an existing event management system to ServiceNow ITOM Event Management. The book provides details on some of the differences that exist between ServiceNow and event management systems that are not integrated with a CMDB. A large part of the book is devoted to the organizational information you need to capture to ensure a successful migration.
It's available on Amazon in paperback or on Kindle.
https://www.amazon.com/gp/product/B08X31Y1B8