My sister is a writer, too. She writes mysteries (Kirsten Weiss, check her out!). As The Lady Who Knew Too Much releases in two days, I was starkly reminded of how different my writing style is to hers.
She is going through the final edits for a book that will be releasing in one year. She has the cover, the back cover copy, everything ready to go. She'll release it as a preorder soon, and spend the year marketing it as she writes other books.
I put TLWKTM on preorder a month ago, while I was still finishing writing it. Raced through edits these past two weeks. And just got it uploaded to Amazon and the other publishers with 22 hours to spare. :)