I really enjoyed this books approach to object-oriented programming. It’s focus on the consumer-supplier relationship and the decisions needed to ensure that the supplier is well positioned to support change is very well written and worked into examples is useful ways.
Done great insight on a simple approach to designing classes, libraries and applications using these ideas made the time reading this book well worthwhile.
Personally, I wouldn’t be discouraged by the discussion on Smalltalk and Objective-C. There are great insights here drawn from each language that are useful everywhere.