Books that are published in paper format, titles should fit on the spine of a book.
Books that are only published in electronic form, titles may work best if they contain enough information to catch people browsing a list.
My pet peeve is not so much long descriptive titles but publishers like Joffe Books, who pad out the titles with such meaningless material as "a gripping murder mystery full of twists" (see
https://www.amazon.ca/dp/B0DNR615PV ).