In my time I've read - and even managed to finish several books of philosophy, but apart from Karl Popper, have always found them hard going. Warburton's book (2011) is clear, reader-friendly and comprehensive, beginning with a few pages on Socrates and proceeding on through Roman, Christian, Empirical and Existential philosophers. No chapter is more than 3/4 pages and each little essay is a delight. I picked up my copy in Barnes & Noble in NYC a week ago and managed to read a little chapter between subway stops. I now know a bit about the Stoics, the Sceptics and the Christian philosophers, as well as Machiavelli and Nietzsche.