Marketing of an electronic book of ethical hacking?

Hello,

What are the best ways to market an eBook in "Ethical hacking"The following things I have tried but because this is a small niche, I have not been able to get satisfactory results.

one. Review of the product through blogs – I have been able to find only some good websites that were willing to offer paid reviews. (Please, suggest me on how to find more.)

two. Affiliates– I have an affiliate program, but it has been a disaster because I do not know where and how to make people willing to sell it.
SEMrush

3. SEO – I've optimized getting payment services by keywords. It is still in process.

Please suggest if you have any other ideas and advice. And mainly, if you have any practical solution on how to get more from paid reviews and affiliates.

Regards,
Sai