Before getting excited, you need to think about exit conditions; tourist guides are not just an extension of fictional inspiration.
Their role is to provide a practical mandate and manage the downside of unforeseen events, which is a separate and much later step in planning.
A novel can make you dream of Scotland, but it is the guide that informs you about financial thresholds, complicated transportation, and the lack of network in the Highlands, thus avoiding a regrettable drawdown.
For me, choosing a guide is primarily a fail-safe for a peaceful trip, especially if you don’t have internet access or are uncomfortable with technology, like many elderly people.
Reality on the ground always takes precedence over initial fantasy.