Clear, legible typography
With the rise of online booksellers like Amazon and Barnes and Noble becoming more popular (especially during a pandemic where bookstores have been shut) readers have less opportunity to digest the book in a physical format. It is more important now than ever to ensure the majority of your book cover design elements can be viewed from a thumbnail size, most importantly the title of your book. Ensure your title isn’t too small, or too whimsical that it blends into the background and makes it hard for readers to see.
Bold, contrasting color palettes
A subtitle can be useful to include on the front cover design when your title might need some clarity or descriptive detail. With the rise of eBook popularity it might also help to include a subtitle as it will include searchable keywords that aren’t included in your title or anywhere else upon the cover.