7.5 Test your backup strategy every now and then (nothing is more painful than data loss and dysfunctional backups)
8. "All users lie, there is no exception". Sad but true, get used to it.
9. Automate your infrastructure. If something goes down, just recreate it with Chef/Ansible/Terraform/etc.
[edit: added no.9]
11. Understand the reason the other guy was fired make sure you are not the one holding the bag.
12. Have a issue tracking system in place, you will thank yourself later.
13. Have a change management policy in place.
14. Before you make any change full understand the consequences and have a tested plan to get back to a known good state.
Dependant on what you have to look after you might want more than one book.