Quotations and aphorisms by John Connolly:
There is sometimes a feeling in crime fiction that good writing gets in the way of story. I have never felt that way. All you have is language. Why write beneath yourself? It's an act of respect for the reader as much as yourself.
What is good for you creatively is usually bad commercially. You thrive financially by sticking to a series and not fiddling about too much. You do yourself harm by moving away from the series and the genre. By trying things not based in that particular mode of writing, you will just lose readers.