I have previously posted about downloading free resources from the Mastering Revit books. Here is a link to download the 2013 edition files:
Wiley: Mastering Autodesk Revit Architecture 2013
You can also read some parts free:
Read Excerpt 1 (PDF)
Read Excerpt 2 (PDF)
Read Excerpt 3 (PDF)
Heads-up via tweet from Randy Deutsch