Reading books is not only essential for business but generally in all life aspects. The reason we don't know stuff, is because we don't have time to read. Therefore, I recommend Zlibrary, an online platform you will get all the books for free, from fiction to non fiction, in all fields. OR you can use www.pdfdrive.net. These platforms have millions of books for free download. You do not need to spend any cash buying books. All you need is a phone, internet and time.

Keep reading.