Your look has not been updated yet. I've done more research, the app look will change without needing an update (i guess all the code is still in there).
When you get the updated look, you lose the left side menu (it's just a whole new style... you can google it for screenshots).
Anyway, it's a common issue, and what you can do to temporarily fix it is go into the app settings (in the system settings), and clear Facebook's cache/data.
Doing so will revert the app to its OLD look, where you can log in and set it to most recent (or top stories). Then, when you close the app and reopen, facebook will "update" to the new look.
I believe the new look only enables to certain users at the time (it's a rolling update). It's interesting how both looks are programmed into the same version of Facebook.
Here is an article disussing the new look. The new look is now included in the final builds of Facebook available in the Play store, but only certain users are being transitioned to it.
http://www.androidauthority.com/facebook-alpha-337296/
