While reading up on granite installation, the
book indicates that granite and marble pros install with silicone rather
than mortar.


I have installed marble on the floors and walls of my bathrooms with no
trouble and plan to use mortar for my granite over a bed of 3/4" plywood
covered by a 1/2" layer of backer board. Should I investigate this
silicone thing further or just go with my original plan?


Nah, they wrote a book about what the pros use but I'd bet you know more
than them.