What was the deal with Haruhi's Endless Eight? In Haruhi second season, there was 8 episodes that have been the same. The series of "Endless Eight" episodes are literally doing the same things over and over again. But it's not really the same thing, they re-animating and re-dubbing whole episode, they didn't being lazy and use the same source.

Here's the same sequence of different episodes when Haruhi called Kyon to ask him to swim with others at the pool:



As you can see they give different tones, angles, outfits, etc. That's too much effort for same situation all over the episode for eight episodes straight. So why did they doing it? Did they also did it in light novel? What is the point of "Endless Eight"?
Most likely the last arc of the show was originally planned to adapt The Disappearance of Suzumiya Haruhi, but the producers changed their mind well into production, and decided to make it into a movie instead. As a result they had to fill in a seven episodes gap that they already bought the timeslot for, thus this gimmick was born.

They Endless Eight chapter in the novel is only about the very last iteration where Kyon figures out the solution.

The point of Endless Eight was to provide a reason for Nagato to do what she did in Disappearance, being the only one to remember the over 15000 iterations.