/sci/ - Science & Math

Hello /sci/, how do I learn about PCA? I have a classification problem and I know PCA is probably the best way to sort it out given the data I have. I have an intuitive understanding of what PCA is (taking a big data cloud and finding the axis with the most variance) but I need to understand its nuances as a tool so I don't make any dumb mistakes and can talk to stats experts in a knowledgeable way. I also need to understand clustering better. Any book/article recommendations about how to use PCR as a tool without getting too bogged down in the theory?