add a better README

README.md

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-# Setup
+# Halo Hero
+
+This book is a course on [Halo2](https://github.com/zcash/halo2) development and PlonKish arithmetization in general.
+The intended audience is Rust developers who have a vague understanding of succinct proofs in general,
+but no specific knowledge of Halo2, PlonK or developing circuits for zkSNARKs.
+
+The book was created as a collaboration between [ZKSecurity](https://zksecurity.xyz) and
+the [Zircuit](https://www.zircuit.com/) development team.
+All material, full code examples and the book's source, are available on [GitHub](https://github.com/zksecurity/halo2-course).
+
+![zks](src/intro/zks-scale.png)
+
+![zircuit](src/intro/zircuit.png)
+
+## Running The Book
+
+The book is build using `mdbook` and `mdbook-admonish`:
 
 ```
+cargo install mdbook
 cargo install mdbook-admonish
+mdbook serve
 ```
-