Associative algebras and their representations
Hazewinkel, Gubareni, Kirichenko, Algebras, rings and modules, vols 1 & 2
Pierce, Associative algebras
Assen, Skowronski, Simson, Elements of the Representation Theory of Associative Algebras
Auslander, Reiten and Smalo, Representation Theory of Artin Algebras
Curtis and Reiner, Representation Theory of Finite Groups and Associative Algebras
Etingof et al, Introduction to representation theory
Benson, Representations and cohomology, vols 1 &2
Crowley-Boevey, Representations of quivers
Special subjects
Frobenius algebras
Skowronski and Yamagata, Frobenius algebras vols I and II
W-algebras
Reviews:
Arakawa, Introduction to W-algebras and their representation theory
Principal
Zamolodchikov, Infinite additional symmetries in two-dimensional conformal quantum field theory
Feigin and Frenkel, Quantization of the Drinfeld-Sokolov reduction
Bouwknegt and Schoutens, W-symmetry
Dickey, Lectures on classical W-algebras
Non-principal
Kac, Ruan and Wakimoto, Quantum Reduction for Affine Superalgebras
Gan and Ginzburg, Quantization of Slodowy slices