I lived in Shetland for a short while in the seventies and have been visiting ever since, so I have lots of useful contacts!
Shetland's influences are far more Scandinavian than Celtic.
Television is much more collaborative in many ways than prose.
You must never call it the Shetlands. Islanders are proud and can be prickly about the name: it's either Shetland or the Shetland Islands.
A writer loses possession of her work as soon as it's reaches its audience. Each reader brings his own experience and prejudice and imagination to the work. Television adaptation just goes one step further, and the novelist has to learn to let go.