Ask HN: In-depth posts on interesting topics?

I usually spend about two hours every day doing research. Mostly, I do books; spending a few weeks or months on a topic. From time to time I have a free day, or I want to dip my foot in the water and see if I like the temperature before jumping in.

I’m looking for in-depth tutorials, posts, and even short books, that can be completed in less than a day (or two), and offer a decent exploration of the topic they’re dealing with.

Some examples I liked:

- ANNs: http://karpathy.github.io/neuralnets/

- Music Generation: http://teropa.info/blog/2016/07/28/javascript-systems-music.html

- Logs: https://engineering.linkedin.com/distributed-systems/log-what-every-software-engineer-should-know-about-real-time-datas-unifying)

- Encoding: http://kunststube.net/encoding/