Thanks for sharing and the effort put in so far. After a quick glance over I think you should consider giving at least a glancing mention in your intro section

Thanks for sharing and the effort put in so far. After a quick glance over I think you should consider giving at least a glancing mention in your intro section to the importance of hardening SSH itself vs the typical default install. It doesn't need to be much since it's somewhat out of scope of your specific focus here, but it'd be worth a few sentences mentioning the value of keys over passwords (and disabling passwords entirely), that keys can be kept on tokens as well (YubiKeys/NitroKeys for example), value of disabling ancient ciphers, that sort of thing. You say the book assumes "some experience with SSH", but given your stated audience includes admins/devs/blue team as well (and in another comment I see someone talking about using it with students) and I've seen a ton of really bad SSH setups used there, I think even a sentence or two about assuming hardening as well to get people into search engines (if you don't feel like more) would be valuable in the context of intrusion response.