I'm going to mention and give some links to Projective Geometry books and pdf's. (Since, the idea of pole-polars are used the most in olympiad problems, I'll give some links seperately about that as well.)
I hope others will continue the thread.
$[1]$
Projective Geometry, by,
H.S.M. Coxeter$[2]$
An Introduction to Projective Geometry, by,
Bobby Poon$[3]$
Projective Geometry, by,
Milivoje Lukic$\quad$A note from IMO-Math
$[4]$
Projective Geometry, by,
Alexander Remorov $\quad$PDF from Canadian IMO Training
$[5]$
College Geometry, by,
Nathan Altshilier-Court, $[6]$
Advanced Euclidean Geometry, by,
Roger A. JohnsonThese 2 books have a brief introduction to pole-polars. (The treatment in Court's book is more thorough.)
$[6]$
Pole and Polar, by,
Kin Y. Li$\quad$Mathematical Excalibur, Vol.11, No.4
$[7]$
Pole-Polar: Key Facts, by,
Tarik Adnan Moon