You need to make a will.
To make sure that your partner/ spouse/ children/ etc. understand what your wishes are so they can make decisions.
Especially, if you are a writer, you need to have a will that spells out who should handle your literary estate. You probably will still have royalties coming in. Your executor needs to know who to contact to inform them of your death and where to now send royalties. Yes, some of your books will still be earning income long after your death.
Margaret Wise Brown's Goodnight Moon, published in 1947, is still gathering royalties. Yours might not stay popular that long, but still - there will be rights and royalties that have to be handled by your executors.
Neil Gaiman has suggestions for you, plus a link to a PDF of the form you will need.
Click and read and learn.
And Make A Will.