I think both of these paragraphs are a bit wordy. All we need to do here is explain what an invokable is (it should then be obvious why that will no longer work), and then explain factories. I'd suggest replacing these two paragraphs with:

> An `invokable` is a class that can be constructed without any arguments. Since our `Album\Controller\ListController` now has a required argument, we need to change this. The controller manager also support using *factories*. A factory is a class that creates instances of another class. We'll create one for our list controller. Let's modify our configuration to remove the invokable, and add the name of the factory instead:

Also, personally I would just do this as a closure in the module's `getControllerConfig()` - do we have any explanations on when to use factory classes and when to use closures?