Assuming a major chunk of your books books are shared between youze All
An alternate is to add a
Tag to the books uploaded.
"OnHers", "OnMine"
and create a VL (template) to show which.

Kovid how hard would it be to create a Tag as part of the send to Device process . The defined tag would be per device (

serial#, a value set/stored in the driveinfo.calibre on each device )