Show HN's are for getting feedback, first and foremost. If there's no free functionality, then people can only give feedback on your business model, not your actual product.
Show HN is for something you've made that other people can play with. HN users can try it out, give you feedback, and ask questions in the thread.<p>On topic: things people can run on their computers or hold in their hands. For hardware, you can post a video or detailed article. For books, a sample chapter is ok.<p>Off topic: blog posts, sign-up pages, newsletters, lists, and other reading material. Those can't be tried out, so can't be Show HNs. Make a regular submission instead.<p><a href="https://news.ycombinator.com/showhn.html" rel="nofollow">https://news.ycombinator.com/showhn.html</a>