Every piece of writing needs a hook that works like a subject line. Name your audience explicitly in it: instead of just "Multiple Streams of Income," write "Multiple Streams of Income for CEOs." That specificity makes readers feel the piece is for them.
If they're going to be writing anything, whether it's an email for engagement or whether it's a book, you need a good hook. So two rules about writing, whether it's an email or a book, is the subject line. And that's like the title on the book is the same thing as the subject line. It gets people to open the book or open the email. A hook is something that intrigues people and gets them to want to look further. And the other tip is, who are you wanting to open this? Coaches, entrepreneurs, corporate structure like CEOs. Who do you want to open it? Put that there and say CEOs, multiple streams of income for CEOs, right? And then multiple streams of income becomes, oh, I'm interested in that. It's a hook. And CEO is, it's for me because I'm a CEO, or it's not for me, I don't want that. So being very clear on your ideal customer, and that makes a good book title and it makes a good subject line for your email.
