I like to read books/authors in the order they're written. I'm sure I'm not the only one who does this. Even if an author doesn't write a series, I still like to read the books in order.
Part of this is being able to see/read the evolution of the writer as they progress. Usually you can feel when they find their voice and the story seems richer than the previous books. I love that! Having felt it in my own writing it's something to see it in someone else's.
In the case of a series, you can watch the development of the character in a fun way. See them mature, grown and evolve as the series goes on. As the author feels more at home in their own skin so do their characters.
Just a fun little habbit. Annoying when I accidentally pick up the second book and have to put it aside until I can get the first one. I know, a little compulsive, but what can I say? Anyone else out there like me?