The new Android N-ify module brings at least some of the Android N enhancements to devices running Android 5.0 Lollipop or 6.0 Marshmallow. Right now, Android N-ify brings the notification bar, drop-down, quick settings tiles, settings app, and Recent apps UI in line with Android N. And, it also brings the fast switching to your last app by double tapping the Recents button.
The developer also has plans to add Night Mode, Doze mode when the device is moving, hamburger drawer in the Settings menu, and emergency info on the lockscreen. Overall, N-ify seems solid, though there are some bugs so you'll have to be careful about that. Otherwise, you can get some Android N on.