As an avid reader, I often pick up new series. They might not be newly released - with some it might be years since the first book was published - but most of the time, they are books in a series that is not fully published yet. There might be one, three, ten books coming out in the future, and as a collector, I always like a complete set of books with matching covers.
Unfortunately, there seems to be a facelifting trend in YA lately. Some of my favorite not-fully-published series have gotten a makeover, and while I totally understand that sometimes you just need a new haircut, haircolor or a new wardrobe, I wish you would consider that there are readers around who bought the books when they first came out. They buy the book(s) with the original cover(s), and most of them prefer to have a matching set. There are always readers who don't mind a change in the look of the next books, but I'm not one of them.
Some recent examples that affect my collection are the Delirium trilogy by Lauren Oliver, the Curse Workers series by Holly Black and the Dustland series by Moira Young. From all three, I have (at least) the first book in the original cover, and because of the makeover of the entire series, my sets won't match. When I read about another series getting a makeover, I often feel like publishers aren't thinking of the fans who bought and read the book when it first came out. I know this is not the case, but it bothers me - when I buy books that are part of a series, I always make sure that I have the covers in the same style (for example, that I order the US covers or the UK covers instead of randomly picking an edition) and my OCD does not like it when I have books in different shapes, sizes, and styles.
To be quite honest, I hate cover changes when not all the books are published yet. The Uglies series by Scott Westerfeld was revamped, too, but at least that happened after all the books were published. In that case I don't mind so much: readers who have been following the series since the beginning (or have only picked it up before the last book was published) have enough time to buy matching copies and new fans will have the completely new covers. In theory, this means that everyone can have a matching set of books.
But when new covers are released just before the last book comes out, or months after the first book was released, readers won't have the choice to go with the new look of the series. And that bothers me. I wish I had the chance to decide if I wanted my set to match with the original covers, or purchase a completely new set. And often, I don't have that chance. I can totally understand that publishers give a series a new look to boost the chances of someone picking up the book. I get it. But it bothers me, and I wish I had the chance to choose.
There are only three options for me: settle for a set that won't match and drive my OCD crazy, selling my old copies and buying a completely new set of books, or, which is most likely, give up on the series altogether. This is punishing the author and I really don't want to do that, because the author has nothing to do with the decision to re-do the cover. But sadly, this is what happens. As I now own a Kindle, I might pick up a digital copy in the future instead of buying a physical copy, but that's not the solution to my problem - it's just avoiding the issue and hoping it goes away.
My hope is that you'll consider the earliest fans of the series. That you'll realize that there are people who are not happy with the changes you made in the look of the books. That you'll realize that you might win some new readers, but you might be losing some of the older ones. Like me.