This book covers two areas of computer technology: creating USB based mass storage systems, using either rotating (disk) media or flash storage. It offers guidance and examples for each of these with a focus on the special requirements and limits of embedded hosts that access USB storage devices.
A design engineer who's task it is to design a USB based memory subsytem has options. He or she can contact various device manufacturers, request data sheets, and demo or development boards. This step will be needed. Next is to prototype several such devices, to create software drivers, and to debug the hardware and software. One could "google" for sources, and start there, or... One could purchase Jan's book and get a head start with both hardware selection AND with software driver development.