I always look into the internals of libraries I use, it's usually easier, and faster than reading the documentation. Sure, there are some libraries that so advanced that it makes this difficult, but you should still know what it's doing, and how the code is organized.

The idea of an abstraction layer is to make it easier to read and write code that is at a different layer. Many of us write our own abstractions, it's not because we don't understand what its doing.