These are my absolute holy-grail book suggestions for all things digital marketing, human psychology and business. These books contain actionable advice and visual examples which is why I've listed them (no boring books with chunky paragraphs).
This one has all the basics with great examples that teach you how to write well (by cutting the fluff)
Everybody Writes: Your New and Improved Go-To Guide to Creating Ridiculously Good Content|Hardcover
Teaches you how to find your brand's unique value proposition and position yourself in a crowded market.
Positioning: The Battle for Your Mind by Ries & Trout
Another great book that teaches you how to write good content that is specific and straight to the point. Also has so many examples for each point so you know how to apply the principles.
The Copywriter's Handbook: A Step-by-Step Guide to Writing Copy That Sells (4th Edition)|Paperback
This is a classic that teaches the psychology of human behavior and how to market to them.
Influence, New and Expanded: The Psychology of Persuasion|Hardcover
Teaches you how to make money with your passions and skills. You will learn how to identify what you're good at, find a profitable idea and how to market it and make money with it.
How to Get Paid for What You Know: Turning Your Knowledge, Passion, and Experience into an Online Income Stream in Your Spare Time|Hardcover