Microsoft released a free 510 page e-book about SharePoint 2013
Preview. Recently , Microsoft announced that SharePoint went officially RTM, but I believe most of the contents of this book will also apply to the RTM version.
This book covers everything that an IT pro needs to know about SharePoint 2013. It starts with how to design your farm, and how to install the servers and prerequisites all the way to how to configure your Service Applications and configure Resource Throttling.
You can download the e-book here: