Click the dropdown box labeled Display at the upper right. Hybrid view works best. In my opinion, topic view is awful. You can't see if there are new posts in the thread, you have to show the whole damn thread to read just one small section of it, and it's a ***** to tell who's replying to who.
Strange, I don't see that box unless I'm in a thread. Click Forum Actions at the top, then General Settings, and you can scroll down to it.