Facebook advertising can be a good way for self-published authors to promote their books and reach a wider audience. However, the return on investment (ROI) for Facebook advertising can vary greatly depending on a number of factors, including the target audience, the quality of the ad, and the overall effectiveness of the advertising campaign.

To maximize the ROI of your Facebook advertising campaign as a self-published author, it is important to:

1. Clearly define your target audience: Identifying the demographics, interests, and behaviors of your ideal reader will help you create ads that are more likely to appeal to them.

2. Create high-quality ads: Make sure your ads are visually appealing, well-written, and aligned with your brand.

3. Test and optimize your ads: Use A/B testing to determine which ads are performing the best, and make adjustments as needed to improve their effectiveness.

4. Set clear goals and track your results: Determine what you want to achieve with your advertising campaign (e.g. increased book sales, more newsletter subscribers) and use Facebook's analytics tools to track your progress and measure the ROI of your ads.

Overall, Facebook advertising can be a powerful tool for self-published authors, but it's important to approach it with a strategic, data-driven mindset in order to get the best results.