In the Scrum Body of Knowledge you can read the complete theory about the Agile Scrum framework from A to Z. From the principles of Agile and Scrum, via the various Scrum roles to details. For example, about estimating the risks of projects by Scrum Product Owners. And the effective organization of teams by Scrum Masters.
This completely revised fourth edition (2022) also offers two additional chapters on scaling and applying Scrum for large projects and organizations.
The SBOK was developed as a guide for professionals and organizations that want to apply Scrum and as a reference work for everyone who is already doing so. It is based on the Agile Scrum theory and the experiences gained in thousands of projects in all kinds of companies and organizations. Many Scrum experts have therefore contributed to the development.
You can request it here for free as an e-book.