Thanks for your interest in Head First PMP. If you purchased the ebook from oreilly.com you can then get the newest edition for 50% off. You can also register your print book on oreilly.com and get the new print version for 40% off or the ebook for 50% off. Here are more instructions on how to do this:
"If you have an older edition of a book, you can receive 40-50% off the purchase price of a newer edition.
Register your book at oreilly.com, and we'll send you a 40% upgrade discount for print books and a 50% upgrade discount for ebooks when we publish a new edition.
View a complete list of your registered books in the Books section on Your Products page.
Note: Books published by Wiley, Wrox, Sybex, For Dummies, Visual, dpunkt, O'Reilly Verlag, and Microsoft Press Deutschland are excluded from this offer"
I hope this helps and have a great day!
Customer Service Representative