What I appreciate about books like this is that they assume the reader is already familiar with programming, and so the book cuts to the chase and explains why this language is unique and how it is different from the languages the reader probably already knows. The author was smart enough to know that very few students of F# will have picked F# as their very first introduction to programming, so this makes a lot of sense. I get frustrated with programming language tutorials that take the opposite approach and expend multiple screenfuls carefully explaining what a variable is.