I'm going to recommend something that totally misses your criteria above because i imagine you're looking for some sort of comprehensive text book.

Sophie's World by Jostein Gardner. Read it ages ago and it basically gives an introduction to philosophical ideas while being packaged in a novel within a novel form.

http://en.wikipedia.org/wiki/Sophie%27s_World

No.

All that summary does is let you in on the vehicle by which the different philosophies are introduced to the reader.

While it serves as an introduction to philosophy, it also forces the reader to understand the underlying principles behind them.

While 2+2=4, it doesn't just let you accept that 4 is the answer but instead it makes you understand why 4 is the answer. It is still a relatively 'easy' read but it is quite exhausting because it introduces so many new and different concepts to someone who has not read up on philosophy beforehand.