This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
"Agile Software Development" by Robert C. Martin and "Refactoring" by Martin Fowler are the two books that made me grok what OOP is about. Both make use of UML, and the former also has a short introduction in an appendix.
In fact I think every serious OO developer should read at least those two books. But that's just me...
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus