There is a new edition of the book and this is an old link.
Constants are always immutable, and may only be set to a constant expression, not the result of a function call or any other value that could only be computed at runtime.
Global variables are called
const MAX_POINTS: u32 = 100_000; static HELLO_WORLD: &str = "Hello, world!";
You can find the latest version about constants here, and about statics here.