The basic gist of it was that Puck had a crush on Hummel, so he decided to get Hummel to seduce Finn. His reason for helping is that if Kurt gets laid, then his having sex with Quinn is neutralized or something. Puck and Kurt get together in the end, and all this is written in Kurt's POV. The author wrote a sequel in Puck's POV too, methinks.
I think I got most of the tags right? If there are any problems, please tell me and I'll edit this ASAP.