I'm making this post to ask for a reference about combinatorics: I'm a PhD student in representation theory/algebraic geometry. My background is mostly in algebra and geometry (and also mostly theoretical unfortunately).

Right now I'm interested in the cohomology of quiver and character varieties and their links with cohomological Hall algebras, quantum groups and the character ring of $\operatorname{GL}(n,\mathbb{F}_q)$. There's a lot of interesting combinatorics going on, but I really know very little about it. Especially regarding MacDonald polynomials etc.

Outside of the classic book by Macdonald "Symmetric functions and Hall polynomials" what could be a good reference to get into this area of combinatorics? Ideally I would like a book or notes with strong link to representation theory/cohomology theories etc

Algebraic Combinatorics and Coinvariant Spaces. See bergeron.math.uqam.ca/wp-content/uploads/2013/12/book_debut.pdf. $\endgroup$Crystal Bases: Representations and Combinatoricsby Bump and Schilling may be relevant to your interests. They don't focus on cohomology per se, but they do give a very nice combinatorial development of (some of) the representation theory that you allude to. $\endgroup$1more comment