Evaluating the Risk and Reward of Ebook Marketing

Hey everyone!

Just recently, I have published an ebook called Design Systems for Developers. It was my final "brain dump" on the topic of design systems and design tokens after researching the topic for my full-time gig as a frontend engineer.

So far, I've sold 13 copies for a profit of $125.

I trust that the book is solid, but I'm unsure of the best way to promote it.

Most of my sales have come from an influential designer retweeting my launch tweet with a positive review.

I'm wondering how much I should invest in marketing. Some ideas would be to pay for a spot on blogs and podcasts within the niche that the book targets, or a tweet with a review.

What have been your experiences with investing in marketing your book? Is the ROI not worth it? How do you make the decision?