I had lunch with a writer friend the other day and we got into a discussion about what we write. I'm about to be published in historical romance when I really love writing mysteries. She's published in cozies and wants to start a series with a paranormal detective. Conventional wisdom says to write what you know, but there's also the consideration of what will sell versus what you really love to write.
My friend's written two series, one she devised herself and one she was asked to write by a publisher. Her own books practically wrote themselves, while the other series was a chore. I've heard writers speak about being tired of their protagonist or feeling he/she has been used up, but publishers and agents want more of the same.
I guess the question is, do you write for yourself or for a sale? We know where the industry stands, but I admire an author who knows where she stands as well.