There are no books specifically about this.
Three initial points
a) hazardous area classification for the topsides of the FPSO (Zone 0, 1 2) is usually done according to different rules from that of the tanker part (Safe or hazardous). Someone needs to make a unified hazardous area plan for the entire FPSO and everybody should follow it.
b) ships usually use insulated neutral distribution systems - topsides guys usually go for earthed neutral - so the interface between the two needs care
c) the fire and gas detection system and emergency shutdown system applied will likely be far more extensive than on a tanker. It may require the ship's HVAC system to linked into the ESD with remote control.
if you are on a conversion, then the marine and topsides control systems will likely remain separate. If on a newbuild FPSO, someone might try to use a single integrated control system. That's a nice target but takes resources.
Also, the offshore guys might specify
- IP56 enclosure protection for everything, even if it is not on the weather deck
- Ex rated glands for everything, even when in "safe" areas
The offshore guys will look down on the electrical installation on the tanker - but probably won't dig too deep into it. If the hull was commissioned at a shipyard, the topsides electrical commissioning guys may very well try to condemn the yard electrical installation.