One or more of these -
Tom Bingham, The Rule Of Law
Nicholas McBride, Letters To A Law Student
Glanville Williams, Learning The Law
Kenneth Vandevelde, Thinking Like a Lawyer
If feeling brainy, one or more of these -
Ronald Dworkin, Law's Empire
HLA Hart, The Concept Of Law
Frederick Maitland, The Forms of Action at Common Law
John Baker, An Introduction to English Legal History
Andrew Riggsby, Roman Law and the Legal World of the Romans
For human interest stories about shenanigans in high and low places -
Misha Glenny, McMafia
Tom Wright and Bradley Hope, Billion Dollar Whale
Alex McBride, Defending The Guilty
Anon, The Secret Barrister