I just found out that coming out sometime this fall, is a book called Ted and Ann by Rebecca Morris. It’s about the 1961 disappearance of Ann Marie Burr and also about Ted Bundy and what, if any, role he played in Ann’s apparent kidnapping. The book’s website has an excerpt and also pictures — finally, a decent quality photo of Ann Marie!
[UPDATE: Holy cow, another good photo!]
I don’t see a precise date of release. The book is self-published, so I don’t know if it’ll be available through Amazon, but it looks like you will be able to buy it off the website anyway.