Olympiad Geometry Problem #39: Circumcenter, Incenter, Double Segment

Here is a very beautiful problem involving the segment connecting the circumcenter to the incenter, and just a few other lines. It is from the Sharygin Geometry Olympiad in 2016. Enjoy! Link below.

[omparkash-njzy]

Pls close left side panel, if you simply use redo button in the whole vedio, it will increase visibility area.

Would you suggest me a book others than EGMO by Chan or other sources for learning elegant solution of geometry for Olympiad.