The Fine Art of Brewing - start by opening one hint at a time to see if it's enough information
Some inks can only be seen with a certain type of light.
Try scanning the cover with the UV light.
When shinning the UV-light on the page with the cover for "The Fine Art of Brewing", you should now be able to read 1 + 4.
The right number and fourth digit in the code for the USB-stick is therefore 5