Analytical Philosophy
These books represent some of the important and accessible work in "analytic" philosophy.

They're a bit more academic than most of the books on this site, but anyone who can vaguely recall an undergraduate philosophy course ought to be okay. In particular, most assume a knowledge of logic, although you can get by with a very basic unstanding of the symbols.
Naming and Necessity (Library of Philosophy & Logic)IndividualsOn the Plurality of Worlds
Naming and Necessity (Library of Philosophy...
by Saul Kripke
£18.32
Individuals
by P.F. Strawson
£19.94
On the Plurality of Worlds
by David Lewis
£17.89
Inquiries into Truth and Interpretation: Philosophical Essays Volume 2 (The Philosophical Essays of Donald Davidson (5 Volumes))Word and Object (Studies in Communication)
Inquiries into Truth and Interpretation: Ph...
by Donald Davidson
£17.99
Word and Object (Studies in Communication)
by Quine
£20.56