If people ask me for the ingredients of success, I say one is talent, two is stubbornness or determination, and third is sheer luck. You have to have two out of the three. Any two will probably do.
The same tools that make any writer good, plus a cheerful willingness to suspend belief.
The comments I most appreciate come from ordinary readers who've happened on one of my books at some time of stress in their lives, and who actually credit the book with helping them through a bad time. It's happened a few times in forty years.
The Berserkers have been with me for about forty years, and we're not done yet.
The advice would be the same for any kind of fiction. Keep writing, and keep sending things out, not to friends and relatives, but to people who have the power to buy. A lot of additional, useful tips could be added, but this is fundamental.
My gut feeling is that paper and ink are going to be with us for a long time yet, and in substantial quantities, though certainly books are now going to be available in other forms.
Research is of considerable importance in certain fields, such as science and history.
More immediately, I'm currently working on another Dracula in which there will be connections with ancient Egypt. That's about as far as I want to go in commenting on current work.
Mysteries I read for fun, so I will probably never write one, for fear of spoiling the fun.
Only towards the end of this process are any of the chapters in fully readable condition, a state of affairs that used to alarm my wife. But Joan's got used to it.
Probably all the books I've ever written have been efforts to define the boundaries of humanity.