The book "Exploring Arduino - Tools and Techniques for Engineering Wizardry" by Jeremy Blum is a companion book to a set of YouTube tutorial videos that provide a very good introduction to the Arduino platform.
Link to Jeremy Blum's Homepage
Link to Jeremy Blum's Arduino Tutorial Series
Instructions on how to gain access to the ebook
Step 1. - Go to UML Library page and enter Arduio as the keyword
Step 2: Select the option "View Now" for the listing for "Exploring Arduino..."
Step 3: If you are off campus, you will need to log into the UML Library system using your UML email address and password
Step 4: You are then directed to the ProQuest ebrary site and you have the options to either "Read Online" or "Full Dowload". The full download requires you to download and install "Adobe Digital Editions" which will allow you to use the downloaded copy for 14 days.
Step 5: The online reading interface is quite robust and the book figures are in color - which is a big bonus over the print edition.