I would like to know a reference for Grothendieck duality in a resolution of singularities. More precisely, let $Y$ be a normal, Gorenstein variety with finite quotient singularities, and suppose that $f\colon X \to Y$ is a crepant resolution of singularities, meaning that $f^*\omega_Y \cong \omega_X$. In particular, since $Y$ is normal, we know that $Rf_*\mathcal{O}_X \cong \mathcal{O}_Y$.

Then by general result there is a functor $f^!\colon D^b(Y) \to D^b(X)$ between the derived categories of $X$ and $Y$ which gives an isomorphism

$$ Rf_*R\mathcal{Hom}(F, f^! G  ) \cong R\mathcal{Hom}(Rf_*F,G) $$
for any $F \in D^b(X)$ and $G \in D^b(Y)$

My question is: is there nice description of $f^{!}$ in this situation? 

I guess it should be related to $Lf^*$ and the relative canonical, but I dont know much about this topic.