Book subtitles are getting longer because of SEO

Amazon allows up to 199 characters for a book’s title and subtitle combined, making the word combination possibilities, if not endless, vast. Karen Rinaldi’s self-help book “It’s Great to Suck at Something: The Unexpected Joy of Wiping Out and What It Can Teach Us About Patience, Resilience, and the Stuff that Really Matters” started out with a shorter subtitle: “The Exceptional Benefits of Being Unexceptional.” (Dutton)
Pelz said the final wordy subtitle was chosen to try to convey to readers: “We know, sucking at something sounds a little crazy.

Source: www.washingtonpost.com