Sales for Series 

I've been told over and over by authors and publishers that a series sells much better than a standalone. Supposedly, a series leads to multiple books selling while a standalone is only one. Although this makes sense, I haven't found this necessarily true. 

My two best-selling books on Amazon are standalones -- Mountain Mishap and When Winter Is Past. Mountain Storms, the first book in my recent series, In from the Storms, is beginning to also do well, but it's too early to tell if it will lead to sales of the other two books in the series or not. Most months, Mountain Mishap and When Winter Is Past continue to outsell all the other books combined. They have been phenomenal, and I wish I could figure out their secret. 

I recently did a poll asking if I should introduce a novel in the planning stages as a standalone or part of a series since it could be done either way. Overwhelmingly, three-fourths of the people said a series is best, but my experience makes me question this. I'm wondering if releasing standalones isn't better unless some of the same characters appear in all the books. I also wonder if other well-published authors have had similar experiences with series and standalones.

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