After countless reddit recommendations I had to give HPMOR a try and I'm very glad I did. This was the first and likely the only fan fiction I will ever read but I definitely recommend it.

Hard to describe what makes HPMOR work so well. Trying to understand magic using science. Intelligent characters outsmarting each other and acting in their best interest, not the interest of the plot. Teaching readers to think rationally.

Seriously, give it a try.