[docs] Add Linux/Mac instructions for both books

COPYING

@@ -1,7 +1,7 @@
             DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                     Version 2, December 2004
 
- Copyright (C) 2015 Abhay Rana <me@captnemo.in>
+ Copyright (C) 2021 Abhay Rana <me@captnemo.in>
 
  Everyone is permitted to copy and distribute verbatim or modified
  copies of this license document, and changing it is allowed as long

README.md

@@ -4,7 +4,7 @@ Generates a EPUB/MOBI/PDF for the Google SRE Book/s.
 
 Original sources are downloaded from https://landing.google.com/sre/books
 
-Visit the [Releases](https://github.com/captn3m0/google-sre-ebook/releases) page to download the latest release.
+Visit the [Releases](https://github.com/captn3m0/google-sre-ebook/releases) page to download the latest release. Go through all the releases, and click "Assets" to view a list of files.
 
 # Books
 
@@ -44,9 +44,7 @@ $ docker run --rm --volume "/tmp/sreoutput:/output" -e BOOK_SLUG='srw_book' capt
 
 The build for the above Docker image can be audited at <https://hub.docker.com/repository/docker/captn3m0/google-sre-ebook/builds>.
 
-## macOS
-
-Review and run the `generate.sh` script to generate the EPUB, MOBI, and PDF files
+## macOS / Linux
 
 Requirements:
 
@@ -57,6 +55,16 @@ Requirements:
 - `brew cask install calibre`
 - `brew install wget`
 
+Run either of the following:
+
+```bash
+# To download Site Reliability Engineering.
+BOOK_SLUG='sre_book' ./generate.sh
+
+# To download The Site Reliability Workbook.
+BOOK_SLUG='srw_book' ./generate.sh
+```
+
 # Known Issues
 
 - metadata is not complete. There are just too many authors