Best background reading

This idea may have been put forward already, in which case I apologise. I thought it might be useful if we have a thread referring to the best parts of the CFAI material (vs Schweser / Stalla counterparts). So, the idea would be that if you read 5-10 pages of background material which led to a “Eureka! moment”, you could direct other AFers to read it. Of course, this is most useful if you are as specific as possible… Any suggestions?