I passed my Extra exam this past Saturday
My license expired decades ago.
Relicensing some 50 years later has been quite an experience. Note to file: never let my license expire again!
I used these two study aids for refresher material for my Extra exam and recommend both of them highly:
Extra Class 2012-2016 FCC Element 4 Amateur Radio License Preparation by Gordon West
Apple iPhone app: Ham Radio Exam Extra by Roy Watson
Android smartphone app: Ham Radio Exam Extra by Roy Watson
Gordon’s book helps you with the theory behind the correct answers. The app focuses on only the correct answers.
Keep in mind that the current FCC Extra exam will be retired as of June 30, 2016. Order/use the current or new exam depending upon your actual exam timing.
I wish you the very best of luck.
P.S. The real test is nowhere as difficult as it used to be decades ago. Really dumbed down. I was really surprised.