Books from https://archive.org/index.php
If you go to this site https://archive.org/index.php
and search, you will find many very good Catholic books for free and be able to download scanned copies onto your computer.
Type in the Search Box:
Commentary on Canon Law
You should find authors like: Slater, Pohle, Augustine, Manning, Wilhelm and Scannell, Hunter.
If I get time I will put a list together of the ones I have found so far.