I’ve heard this from several writers, especially ones that self-publish children’s books: write books that revolve around a holiday.
With St. Patrick’s Day coming up, I thought I’d post about it. 
In terms of financial success, it seems like series books earn authors the most money. And for children’s books, and probably even for adult books, books around major holidays tend to be “evergreen,” meaning every year people are reminded of the topic, and there’s a chance you’ll see sales spike.
I’ve seen this happen with online articles. For example, several years ago I wrote some short articles for Yahoo! Voices. Some of the articles were about Halloween costumes, others about Thanksgiving and Christmas. And even though I’ve stopped writing for Yahoo!, every year I earn about $10 per month during the big holiday season.
I know $10 doesn’t sound like much, but considering I do nothing to promote that content, and that on Yahoo! I earn $1.75 for every 1,000 page views (meaning my articles get 5,700 page views per month), I think that’s pretty impressive. Part of it might be because I wrote the articles with SEO in mind, and made sure to have catchy, relevant titles. But I think the same technique could be applied to books.
There are a lot of holidays during which certain types of books become more popular: Valentine’s Day, Chinese New Year, Mother’s Day, Father’s Day, Easter, Fourth of July–there’s probably a holiday for every month. It seems like a concept worth exploring.
