readme: adding a better overview

README.md

@@ -1,13 +1,31 @@
-# dir2opds
+# dir2opds - serve books from a directory
-OPDS is an extension of Atom, to serve books. For more information: http://opds-spec.org
+ dir2opds inspect the given folder and serve an opds 1.1 compliant server
 
-dir2opds runs an OPDS server using a directory to generate the feeds.
+# Overview
+ There are good options to server books using opds. I calibre is
+ good at that, but if your server is headless sometimes install calibre
+ just for serve the books don't seems to be the best option.
+
+ That is why calibre2opds exists, but if you just have too many books and
+ you don't want to create a calibre library.
+
+ In that case dir2opds could help you to have an opds server from a
+ directory if you follow one rule:
+
+ - A folder should have only folders or only files (aka books).
+
+ It is ok to have sub-folders.
 
 # Installation
-
     go get github.com/dubyte/dir2opds
 
-#usage
+# Usage
-
     dir2opds -dir ./books -port 8080
 
+# Tested in:
+   - Moon+ reader
+
+# More information
+    http://opds-spec.org
+
+