diff --git a/README.md b/README.md
index c48d23de..c8affb53 100644
--- a/README.md
+++ b/README.md
@@ -56,15 +56,29 @@ After this you can proceed as usual:
 
 Also, refer to the [CONTRIBUTING.md][contributing] file.
 
-### Building the EPUB
+### Building the EPUB and the PDF
 
 Run `make epub`. See `make-cookbook.lisp`.
 
-To exclude regions of text of the build (for example, embedded videos), use these flags:
+You need a decently recent version of [Calibre](https://calibre-ebook.com/). They provide an easy binary installation.
+
+To exclude regions of text of the build (for example, embedded videos that makes no sense in a print format), use these flags:
 
     <!-- epub-exclude-start -->
     <!-- epub-exclude-end -->
 
+Our build script roughly does the following:
+
+- concatenate all markdown content into one file
+- change yaml frontmatters to a markdown title
+- delete the mark regions from the file
+- make internal links work on the EPUB.
+
+It uses some metadata in `metadata.txt`.
+
+We can check the resulting EPUB with `epubcheck`.
+
+
 ## Origins
 
 This is a fork of the [Common Lisp Cookbook][sf], moved from SourceForge.
diff --git a/STYLEGUIDE.md b/STYLEGUIDE.md
index fe07cb2f..ee0eacea 100644
--- a/STYLEGUIDE.md
+++ b/STYLEGUIDE.md
@@ -46,3 +46,19 @@ This snippet...
 ~~~
 
 If the result is large, use another code block, without comments.
+
+## EPUB gotchas
+
+### Embedded content
+
+We should not abuse from embedded content, such as youtube videos.
+
+Please exclude them from the EPUB generation with these flags:
+
+    <!-- epub-exclude-start -->
+    <!-- epub-exclude-end -->
+
+### Internal links (for the EPUB)
+
+We must tweak the markdown links so that internal links work in the
+EPUB reader. See `fix-epub-links.sed` to add your link or just ping us on GitHub.