Q: Purchased books are "no longer available"

I previously purchased the James Bond Collections 1 & 2 and downloaded them to my iphone and ipad.  While reading them on my phone, my ibooks decided to crash all the time.  I deleted the books then tried to re download them to see if that would solve the problem.  The above mentioned books are still listed in my ibooks library but when i try to download them the message "this item is no longer available" pops up.