The 2020 OSINT Handbook is a 509-page list of web links in PDF format. If you were expecting anything more, then you would be mistaken. It covers topics including social media, message boards, people search sites, and government and real estate sites.
Are these links useful? Absolutely! While you have to expect any PDF from 3 years prior to have many dead links, especially when it comes to ever-changing social media related tools, there are many resources here that might prove invaluable that you might never think of using. However, a PDF is probably one of the worst ways of sharing this information. If these links were in bookmark html format, they could easily be searched and added to a browsers bookmark file. However, having them in PDF format makes them kludgy to use and requires that you copy and paste the links directly in a browser.
I want to point out one other positive about this book, it is shared under a creative commons license and that should always be applauded!