A complete description of Safety-II can be found in the book by the same name:

Hollnagel, E. (2014). Safety-I and Safety-II: The Past and Future of Safety Management. Farnham, UK: Ashgate.

The book is available in English, Italian, Japanese, Chinese, and Korean.

A second book describes how Safety-II can be applied in practice, focusing on the use of the Resilience Assessment Grid (RAG).

Hollnaghel, E. (2017). Safety-II in Practice. Developing the Resilience Potentials. Routledge.

The book is available in English and Japanese.