A speaker in a class this past semester, Jeffrey Bauer from ACS – Healthcare Solutions recommended the book "The Art of Clear Thinking" by Rudolf Flesch written in 1951. He said it was the best book written on critical thinking.
Some interesting points from the book:
1. All thinking is the manipulation of memories. Even 'inspirations' are based on your experiences and nothing else. Don't forget that everybody, including yourself, has only his own experience to think with.
2. Your memories are more or less distorted. Your brain registers experience differently from everybody else's.
3. Translation helps your thinking because you use two sets of nerve patterns instead of one. This includes translation of English into other words.
Translating is the ideal form of intellectual exercise. Whenever we translate, we are forced to abandon the mental patterns we are used to and get the hang of others completely alien to our thinking.