Hello! Mind-style is the linguistic representation of an individual's mental perception of the world. To put it simply, mind-style is a description of our personal worldview. My worldview may differ from yours; individual worldviews may be based on personal knowledge, how we process information, our prejudices, our beliefs, our disabilities or challenges, our personal preferences, and even our tendencies towards a particular mode of action.
In the world of literature, a person's world view may also be recognized from an individual's diction; someone who is mentally challenged may exhibit certain distinctive speech patterns. Our recognition of this individual's disability may prompt us to realize that his worldview may differ from ours; quite possibly, he may even exhibit heightened perception in certain areas, superior to ours. His speech may also feature certain transitivity patterns. An example is Benjy in William Faulkner's The Sound And The Fury.
Mind-style in literature is therefore the worldview of the author. It differs from point of view because the concept of worldview is unique to the author.
Another way mind-style can be conveyed in literature is through the use of the conceptual metaphor. For example, in JM Barrie's Peter Pan, Mr. and Mrs. Darling's trepidation in keeping Wendy as their daughter is apparent. She is another mouth to feed; the conceptual metaphor is that children are a financial burden, a commodity, that may or may not produce a positive return on investment.
Mind-style can also be conveyed through the use of faulty logical reasoning. An example is Miss Shepherd in The Lady In The Van. She argues with another character that she knows all about paint jobs because she won a prize for painting while in infant school. We learn later that her rather odd way of rationalizing her argument stems from her involvement in an accident years before. Her guilt and sense of paranoia are the result of this experience; consequently, the resulting negative emotions have impaired her thought processes.
I hope this helps. Please read the link below, as it really explains how Roger Fowler's mind-style concept is used in literature. Thanks for the question.