Subject matter expert with lovely writing
Whenever I start any nonfiction book, I want to know that I'm in good hands. Is this person writing about plants a gardener? Is this piece of investigation done by a journalist? In this introduction, the author manages to quickly convey his specialty (cardiologist), life-long curiosity about bodies, and deep familiarity with genetic diseases. Luckily, the sentences he spend doing this also contain lovely, evocative imagery. At the end of the introduction, you're ready to settle in, confident that you're being led by someone with both authority and enthusiasm.