Because international law is such a broad topic, please visit out International Legal Research Guide for a more in depth discussion.
James Brierly, The Law of Nations. 6th ed. 10th floor - KZ3225.B75 A35 1963
Ian Brownlie, Principles of public international law. 7th ed. 10th floor - KZ3225 .B76 A37 2008
Oppenheim's international law. 9th ed. 10th floor - KZ3264. A3 .I57 1992
Malcolm Shaw, International law. 6th ed. 10th floor - KZ3275 .S53 2008