Book Musings: Re-naming a novel post-publication

Have any of you ever thought about changing the title of your book after it's been published? I think lots of books gets cover makeovers, but it wasn't until recently that I came across two books that got completely new titles. The books are YA fantasy novels entitled Eon and Eona. They have been re-named as Two Pearls of Wisdom and The Necklace of the Gods.

First Novel - First Title

First Novel - Second Title
(Don't these covers just ROCK??)

As a reader and fan of Eon and Eona, I was very confused by this. At first I thought, Hey! Alison Goodman has new books out! Then I read the book descriptions, which were very similar to the descriptions to Eon and Eona, and then I just felt confused. After a little research, I discovered they were in fact the very same stories with new titles.

I also noticed that the book reviews associated with Eon and Eona did not transfer to the new titles.  Eon has over 100 reviews with a 4-star rating. Eona has over 50 reviews with a 4.25 rating. Essentially, the same story has to start from scratch and garner an entire new crop of reviews. (And the new ones aren't all that favorable.) I found this a little sad, considering the number of high reviews the books received under their former titles.

I've played with the idea of changing a particular book title of mine, but I've never actually done it. I think after the little bit I experienced with these books, I'm not sure I ever will, especially since online reviews won't transfer to the new title.

With that being said, what do you guys think there is to gain by changing the title of a book post-publication? These books were published by a main-stream publisher. My guess is they're hoping to improve sales with the new title. But what will a new title do that a new cover won't? I'd love to hear your thoughts on this.