I strongly suggest "Dependency Injection in .NET" by Mark Seemann, regardless of whether or not you're a .NET dev (if you understand basic OOP, C# syntax is generally pretty easy to pick up on).

Really the main reason it's "... in .NET" is because there are a few sections in the book that explain how to achieve DI in some common .NET frameworks, which you are free to ignore. The first half of the book is a fantastic explanation of both the problem that DI solves, and how DI solves it.

I felt like I didn't really understand OOP and the real point of object-oriented design patterns until I read it.