Well, CLOS may be state of the art in very fine designed,exhaustively redefinable, roll-your-own aspect oriented programming, and the most exhaustive object oriented paradigm for the most fluid pragmatic language ever.
But I doubt you'll find useful sources for programming style searching for it.
If you are implementing an object-oriented paradigm for your programming language, it's a very recommendable source to discover what can possibly be done with OOP.
Smalltalk should be a very good source of inspiration, if you're looking for an OOP reference i believe the smalltalk folks have things to say.
Being more of a lisper, I think stateless objects describe problems better suited for functionnal style and pattern matching. Relying on the type system of the implementation is a very unspecified aspect of a language. May be ok though if you know it is fast.
Rubyists still have blocks and closures, bringing in a lot of functional style, almost unnoticed.
The styles are complementary, finding the best one for the problem at hand is the art of program designers.
But I doubt you'll find useful sources for programming style searching for it.
If you are implementing an object-oriented paradigm for your programming language, it's a very recommendable source to discover what can possibly be done with OOP.