C. H. Whiteley 
An Introduction to Metaphysics [PDF ebook] 

Originally published in 1950. For those interested in the fundamental problems of philosophy but not familiar with its technicalities, this book introduces the main type of theory in metaphysics, not by a catalogue of philosophers’ opinions but by a continuous train of reasoning. The central theme is the problem of the relation between Mind and Matter, and in the course of the argument there are discussions of mechanistic materialism, of idealism and our knowledge of the external world, and of the arguments for the existence of God. The problems are presented lucidly but without over-simplification.