Update README.md

Changed the language to be a bit stronger in recommending using the new book over the old books.

Author: Tomer-Eliahu

README.md

@@ -2,14 +2,16 @@
 
 Discover the world of microcontrollers through [Rust](https://www.rust-lang.org/)!
 
-There are currently three versions of this book. All of them provide an
-introduction to microcontrollers and how to use Rust with them.
-The first is older and uses an F3 Discovery circuit board, while
-the second and third are newer and use a micro:bit circuit board instead.
+There are currently three versions of this book. 
+All of them provide an introduction to microcontrollers and how to use Rust with them.
 
-- Read the latest book, using a micro:bit v2:
+- Read the current and best-maintained version of this book, using a micro:bit v2:
   https://docs.rust-embedded.org/discovery-mb2/
-- Read the older book, using a micro:bit (v1 or v2):
+
+There are also two *deprecated* versions of this book. 
+Unless you need to work with a micro:bit v1 or an STM32F3 discovery board, it is *strongly* recommended that you use the new book instead.
+
+- Read the older micro:bit book:
   https://docs.rust-embedded.org/discovery/microbit
 - Read the oldest book, using an F3 discovery board:
   https://docs.rust-embedded.org/discovery/f3discovery