This is a book on the F# programming language.
On the surface of things, that is a nonsensical and/or intuitively obvious statement, given the title of this book. However, despite the apparent redundancy in saying it aloud, the sentence above elegantly describes what this book is about: We are not attempting to teach developers how to accomplish tasks from other languages in this one, nor are we attempting to evangelize the language or its feature set or its use "over" other languages. We assume that you are reading this book because you have an interest in learning the F# language: its syntax, its semantics, its pros and cons, and its use in concert with other parts of the .NET ecosystem.
In order to keep to the core focus of the book, we assume that you, the reader, are a journeyman .NET developer, familiar with at least one of the programming languages in the .NET ecosystem: C# or Visual Basic will be the most common language of choice for those in the .NET community — but if you've learned C++/CLI or even one of the lesser-known .NET languages (IronPython or IronRuby, perhaps, or even one of the dozens or so of "alternative" languages for the CLR), you'll still be able to follow along without too much difficulty.
In particular, we assume that you're already comfortable with concepts like assemblies, managed code, and executing on top of a virtual machine, so none of that ".NET 101" topical material appears here, as it would be redundant to what ...