I have 20+ years of experience in Linux, open source and various applications, framworks and programming languages. I have written 10 books about various IT subjects and 6 of them are on working with Linux. I have written numerous articles for magazines. Both in English and in Dutch (my native language). When writing a book first order of business is to map out the learning path of the reader. After that I write the content, constantly keeping track of this learning path. The language that I use when writing depends on the intended audience. From very informal for students to business focused for more senior management.