One of the best books on OSINT is by Michael Bazzell and is called:
Open Source Intelligence Techniques: Resources for Searching and Analyzing Online Information. This book is highly recommended and an excellent resource for expert or beginner.
For those of you who want to look at it from the opposite perspective, Michael Bazzell has: Hiding from the Internet: Eliminating Personal Online Information which is also excellent and shows how to remove your online footprint.
Other books on OSINT that are worth checking out:
- The era of the lone wolf private eye is over. Julie Clegg’s essential guide to twenty-first century investigations illuminates a bold new path to success in this exciting and rewarding field while effectively debunking the culture of secrecy that has always pervaded the industry.
- Few careers offer the challenges of investigative work and fewer still afford the opportunity to make a real difference. But in the information age, working solo in the dark not only hinders investigation, but threatens the entire industry.