This shouldn't be a hugely controversial topic, but it is. I write to make readers happy. That's my goal in every book I write. How can I make this a better experience? How can I oversatisfy on the premise of their expectations, so they go from liking my book to loving it? That's how you make bestsellers - but most authors consider "writing for a market" or considering the recipient of the work to be selling out of some kind. That's an unfortunate, and unproductive mindset. You need to care about your readers enough to consider their response to your work.