For a while I've been thinking through how best to group books.
Many of you have given me great feedback, thanks!
I've ended up settling on a single system which is working great for me, 'Favourites'.
What I've been wanting to do is collect together my best commentaries into groups based on which book of the bible they cover.
I tried 'Tags' and also "Collections' but neither of those worked for what I needed.
Then I was reminded of 'Favourites' which does exactly what I wanted.
The fact you can 'Rename' the books after you've favourite them was an added bonus as they where coming in with the short name of the commentary, not the full name.
I've added a screen grab just to show what I've done.

The reason for posting was just to share this method incase later someone else is trying to do the same thing.
Thanks everyone for a great Logos community.
In His Grace,
Matt