Come on, CRC cards may be a useful software engineering tool used in agile and extreme programming, they are certainly not central to the idea of object-oriented programming.

I frankly think that Damian's OOP book is very good, it really explains fairly well what OOP is all about.

The only problem is that it is a bit outdated in the sense that it uses the early Perl 5 object-oriented concepts, rather than the more modern implementations offered by frameworks such as Moose, Moo, Mouse, or even Mo, etc. Still, it is a very good introduction to POO concepts.