How This Method Works
The basic principle behind this method is creating a secret "base password" that only you know and then creating a "tag" system toadd on to your base password to create a unique password for each account you create. You'll end up writing down all of your passwords in the book, but no one but you will be able to read them because your base password is always written down as an asterisk (*).
How To Get Started
Shared Accounts? Yeah, you can do that.
But, wait, you have an account that you share with someone. Maybe you have lots of accounts that you share with someone. You need to keep track of those, too. But how???
You have two options.
Have a separate logbook for all shared accounts that both people can access - this is more toward people living/working together.
Each of you keep your own personal logbook and have an indicator (like a symbol or acronym) that shows the account is shared, and therefore uses your shared base password.
Either way, you'll want to team up with your someone to create the shared base password. And determine how you'll be putting the base password together with the tag (base first, tag second or tag second, base first).