The first section of the book matches the blog post you've mentioned but the book also contains other writing from Stephen on the topic and an excerpt from A New Kind of Science.

When looking at this book in the Wolfram media page (https://www.wolfram-media.com/products/metamathematics-foundations-and-physicalization/), I noticed that the titles of the chapters of the book are almost identical to the free-accessible writing about metamathematics (https://writings.stephenwolfram.com/2022/03/the-physicalization-of-metamathematics-and-its-implications-for-the-foundations-of-mathematics/).

Therefore, may I ask, does the book add any more new content about Wolfram's ideas on metamathematics? Or is it a book-version of that writing (almost identical to it)?

When will the Kindle version be released? Wow it’s available now!

Wolfram talks about the physicalization of mathematics and seems to adopt some sort of platonic position saying that mathematics does really exist in some sense or another because mathematics and all the relations between abstract concepts would exist in the ruliad

Thus, I have one question: Since Wolfram says that all possible mathematical concepts and structures would exist in the rulial space, and the ruliad is what makes reality and every possibility is realized by it, couldn't we say that all mathematically possible universes would exist in some way or another according to Wolfram's ideas? (like platonist-physicist Max Tegmark proposed in his "Mathematical Universe Hypothesis" where all mathematical structures would exist as separated universes: https://en.wikipedia.org/wiki/Mathematical_universe_hypothesis)