When you begin your search, you will realize that "Mastercam PDF book" is an umbrella term. To learn effectively, you must identify which type of book suits your current skill level.
Modern versions of Mastercam have a "Help" system based on HTML. However, every help topic has a "Print" or "Export" button. You can compile these into your own custom PDF book focusing on specific tasks, like Surface High Speed Toolpaths .
Start with "Mill 2D" if you are new; avoid jumping straight into "Multiaxis" until you understand coordinate systems and basic toolpaths.