Kenneth Ireland and Michael Rosen's A Classical Introduction to Modern Number Theory also has many proofs of quadratic reciprocity (and many exercises), and covers the cubic and biquadratic cases as well.
quadratic formula | Reciprocity | Quadratic function | Reciprocity Treaty of 1875 | Reciprocity (international relations) | reciprocity | Quadratic equation | Quadratic eigenvalue problem | Quadratic configuration interaction | Helmholtz reciprocity |