Here’s the common advice – book cover titles should be AS BIG AS POSSIBLE to be easily read as thumbnails. If you can’t read it clearly when it’s TINY, then it fails as a book cover.
So many indie authors heed (and demand that I heed) this advice that I generally follow it automatically. But that doesn’t mean I agree! If you look at the book covers that win book cover design awards, the most important thing is the overall aesthetic impression – all the text elements should be small, hidden or smoothly flowing within the picture; they should be part of the picture, not jump out at you. Legibility is not really the key issue. The point of a book cover is NOT to introduce your book’s title to your target reader.
The point of a book cover design is to make an emotional reaction. You want someone to look at a cover and feel those intense interior emotions that good artwork invariably causes. So the first thing you need is a brilliant, beautiful picture/cover design to hook attention. The title doesn’t really matter at all, as long as it looks cool, fits the rest of the design and the genre.
You might say “Well big publishers can afford to be stylish, but we indie authors need bold text to stand out.” FALSE – in fact, since you’re selling online, everybody will immediately be able to see your book’s title in the description ANYWAY – you want them to click on your tiny thumbnail because it invokes interest, not because of the title. And then, the title and subtext will be clearly written on your book’s sell page. So actually, self-published authors who don’t have to worry about grabbing attention from a shelf across the bookstore, have even more leeway with cover design. Take risks! Be daring! Find an amazing, beautiful picture, and add the title simply and strongly where it fits. You don’t need to bevel, drop shadow, or outline text – it should stand out naturally from the placement contrast.
I predict that as indie publishers continue to use bigger text and fonts, “real” book publisher designers will increasingly make simple, small and elegant titles.