I've just redeemed a code for the app and it is just as you expect. You tap the different buttons to make Abe say his lines. Simple. I would LOVE to see the other characters added soon enough because having only Abe just isn't enough
However there is a surprise in the main menu. I ain't going to spoil it because it's actually pretty funny.
E: STM's request
When you speak whilst on the menu, it picks up your voice and plays it back to you in a higher pitch. Basically, Abe mimics you. It made me laugh first time I saw it.