The jurisprudential canon is vast and difficult. One excellent starting point is Edward H. Levi’s An Introduction to Legal Reasoning (1949), which deals, in a clear and straightforward fashion, with fundamental questions about legal reasoning, precedent, and statutory and constitutional interpretation.
Another good introduction, well written and accessible, is Benjamin N. Cardozo’s The Nature of the Judicial Process (1921), which provides the classic (though by no means universally accepted) account of how judges decide cases.
Robert Cover’s Justice Accused: Antislavery and the Judicial Process (1975) is a very readable and extremely valuable examination of the competing claims of law and morality as seen in the historical context of the nineteenth century judicial battle over the legitimacy of slavery.
Lon Fuller’s The Case of the Speluncean Explorers, 62 Harvard L. Rev. 616 (1949), which examines various jurisprudential schools through mock opinions in a hypothetical case, is another classic introduction to the field.