make the intro less scary

src/doc/tarpl/README.md

@@ -2,12 +2,12 @@
 
 # NOTE: This is a draft document, and may contain serious errors
 
-So you've played around with Rust a bit. You've written a few simple programs and
-you think you grok the basics. Maybe you've even read through
-*[The Rust Programming Language][trpl]*. Now you want to get neck-deep in all the
+So you've played around with Rust a bit. You've written a few simple programs
+and you think you grok the basics. Maybe you've even read through *[The Rust
+Programming Language][trpl]* (TRPL). Now you want to get neck-deep in all the
 nitty-gritty details of the language. You want to know those weird corner-cases.
-You want to know what the heck `unsafe` really means, and how to properly use it.
-This is the book for you.
+You want to know what the heck `unsafe` really means, and how to properly use
+it. This is the book for you.
 
 To be clear, this book goes into *serious* detail. We're going to dig into
 exception-safety and pointer aliasing. We're going to talk about memory
@@ -19,21 +19,16 @@ and happy career in Rust.
 However if you intend to write unsafe code -- or just *really* want to dig into
 the guts of the language -- this book contains *invaluable* information.
 
-Unlike *The Rust Programming Language* we *will* be assuming considerable prior
-knowledge. In particular, you should be comfortable with:
+Unlike TRPL we will be assuming considerable prior knowledge. In particular, you
+should be comfortable with basic systems programming and basic Rust. If you
+don't feel comfortable with these topics, you should consider [reading
+TRPL][trpl], though we will not be assuming that you have. You can skip
+straight to this book if you want; just know that we won't be explaining
+everything from the ground up.
 
-* Basic Systems Programming:
-    * Pointers
-    * [The stack and heap][]
-    * The memory hierarchy (caches)
-    * Threads
-
-* [Basic Rust][]
-
-Due to the nature of advanced Rust programming, we will be spending a lot of time
-talking about *safety* and *guarantees*. In particular, a significant portion of
-the book will be dedicated to correctly writing and understanding Unsafe Rust.
+Due to the nature of advanced Rust programming, we will be spending a lot of
+time talking about *safety* and *guarantees*. In particular, a significant
+portion of the book will be dedicated to correctly writing and understanding
+Unsafe Rust.
 
 [trpl]: ../book/
-[The stack and heap]: ../book/the-stack-and-the-heap.html
-[Basic Rust]: ../book/syntax-and-semantics.html