Hey you like Book 2? Cool, good on you, that season catches the most hate and flack out of all of Korra and is considered its weakest part. the general consensus I've seen is that it goes up from there. I like it though, because it actually explains how the Avatar and bending thing came to be while keeping it properly mystical while doing so, and providing a reason why the Avatar might be needed in the future: spirits like Vaatu or Hundun might try to mess with things in the future, and Vaatu himself will eventually come back to try and do this all over again