Poor report book performance for end user

Summary: We have a report book that will run in 2-5 minutes for an administrator, but will time out if run by an end user. How can I trouble shoot this issue to resolve?

Content (please ensure you mask any confidential information): The report book has a table of contents with a nested report book and produces the same report for over 800 entities.

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):