That's a good question. All the options are correct.
Perhaps you would be more likely to choose the present perfect e.g. "have finished" if you have started the books but not yet finished. But really, you could choose either.
The present perfect emphasises the result of an activity, a completed action. So in sentences with "after", it's possible to choose this tense when you want to emphasise the result more than the activity itself. But it's a very subtle distinction and it's not necessary to make it in practice.