I don't want to discard the characters from my mind. The characters might have become my friends, or even my enemies, but I don't want to part with their existence. Oftentimes, a great deal of emotion has been invested in those friend/enemy characters in a book, and turning that last page can make me feel deflated.
That's why I love a good series writer. One book may be finished, but somewhere down the road there will be more. I may still feel a tinge of regret when I come to the end of a book, but at least I know the story will go on in the next volume.
Maybe a series could also satisfy the need for having a collection. I've never had any interest in baseball cards, and collecting something like cars is out of my price range, so books are probably a good alternative. A book series looks beautiful to me all lined up in order on a bookshelf, especially signed copies, but I suppose getting signed copies is an entirely different fascination.
There are many wonderful series for both kids and adults. I enjoy Lemony Snicket and Greg Iles, just to name a couple. I'd love to hear some of your favorites. I hope the series writers keep turning out the books, and I'll be sure to stop by to get my copies signed.