I read on a blog it would be a good way to post on reddit to reach to people interested in this topic.

That blog was wrong. People who recommend Reddit for self-promotion are often spammers.

The author can and should post if believes it is useful for others to read and that's is what this is.

So you don’t actually belong to this community, but you think that you can overturn the long-established rules here? Damn, son. Have some humility.

As the self-promotion guideline says, only 10% of your links max should be to your own content. So, before hawking your book even once, you should have posted at least 9 links to content that you are not personally affiliated with. That is how Reddit works.