Unless your book will be complicated to research or is large in scope, don’t explain who you will write it. Let your proposal prove that you know what you’re doing. If an agent or editor is working with another writer on a similar project, valuable information may wind up in a competitor’s hands. If editors have questions about your research techniques, they’ll ask.
Two exceptions: If your book requires access to celebrities or VIPs, your proposal must prove that you have it. If you’re writing a biography, indicate you access to the person or to the information about the person. If the person is dead, note where the bio will be authorized and whether the estate will give you access to the person’s papers.