This tip isn't appropriate for all of your contacts, but if you discover a book that you find particularly relevant and useful to business people, pass on the title to others.
Because most business people are very busy, especially self-employed entrepreneurs but also high achievers in any industry, and also because there are thousands of books published each month, it is very helpful to get recommendations for useful or inspiring titles. This tip extends to online content as well, including websites, blogs, useful videos, and webinars.
If you read, listen to, or view content you find helpful for your business, chances are you know someone else who will benefit from it. So pass on the suggestion to help your friends gain as you did and strengthen your relationship at the same time.