IMO, the perfective aspect indicates not only some result, but a transition to a new state in general.

Я приготовил ужин. --> the new state is the existence of the dinner.
Вода потекла по руслу. --> the new state is the presence of the water flow.
Я почитал книгу. --> the new state is... hmmm... some piece of the book is now прочитан.

Imperfective verbs are used to talk about processes and states, whereas perfective ones are used to talk about actions, their results and state transitions caused.