I last did an Oracle certification in 2006, that was for 10g. Now I've decided to hit the books and work on achieving Oracle Certified Professional for 12c. But, one step at a time, and the first step is OCA. Below is a comparison between my old 10g book and the new 12c. I haven't done a thorough compare and contrast, but it's from the same publisher, and the text is the same font size. Looks like there's just that much more content!