For those of you seriously interested in learning Arabic beyond the mere basics, I strongly recommend using “Arabic Between Your Hands”. This 3-volume series was developped by for PhD’s in Saudi Arabia and of all the books I’ve seen to learn Arabic, these are by far the best. 

The series assumes that you already know the Arabic alphabet and understand how to read in Arabic. You will need an Arabic-speaker to helo guide you through the lessons. I learned with these books on my own (with a good dictionnary), but occasionally needed the help of a native speaker to answer specific questions or decipher word-forms that might not have been in the dictionary.

The books are available for download here. 

Enjoy!