I wrote a book with Mikko Vermanen and Jani Koskinen, called Kyberturvan pelisäännöt pienyrityksille (Ground Rules of Cyber Security for Small Businesses). It was published by university of Turku, and is freely available online (in Finnish).
The book includes basic information on cyber security management—how to conduct a risk analysis, manage strategic components of information security and assess its current state. It also lists the generally adviseable ground rules of cyber security, such as timely software updates, password policies, having backups and enabling MFA on important accounts.
We released the book under the Creative Commons Attribution 4.0 license, and I uploaded the manuscript in Markdown format to GitHub, so that everyone can participate in keeping it current.