Pager Duty's Social Engineering Slides
Admittedly, there's probably a lot of other great sh*t out there, but I did not do too much exploring this year. Nonetheless, this presentation is great to view on the important topic of social engineering. Beyond that, it's a fantastic example of a presentation that tells you just enough to be affective while being digestible to a wide audience of both technical and non-technical folks.
Best Book: Effective Python
Due to a change in job, 2019 was the year I went from being a JavaScript programmer to a python programmer. While headfirst Python Did an amazing job with getting me up to speed on python (seriously check it out), effective python gave me a cornucopia of design patterns that are effective in so many production-level situations. Finally, I understood that "Pythonic" has some practical meaning and isn't just something python devs throw around to be different.