But I say unto ye, "Umm, why not?"

Book cover design is both a science and an art, one that thousands of people have devoted their lives to.

And the main thing they try to do with this occupation is this: make it easy for us readers to judge the book by the...well...cover.

You only have to wander through a bookshop or a library (depending on your budget or attitude to consumerism) and pluck a book from the romance section, one from science fiction, and one from the literary shelves, and then compare them.

The romance one will almost always feature a photograph of a person, and sometimes two (the romantic couple, naturally). It will have flowing writing, pastel shades, a lot of white and maybe a mansion or a beach on the background. (Heaven forbid the romantic heroine lives somewhere that is not picturesque.)

Mind you, sister genre chick lit doesn't do photos. It's really all about quirky illustrations, bright colours and fonts that are variations on Comic Sans. That's because modern love can be super-hilarious.

Sci-fi involves lots of black, something unidentifiable but metallic, spacey graphics and often faint, random text in Courier New. I don't know why it's Courier New (do future civilisations only communicate by typewriter?) but it always is. If you're lucky, you get a disembodied head that look a bit robotic.

Fantasy is often thrown in with sci-fi, but I'm not even going to attempt to outline the fantasy tropes, as fantasy fans might attack me with their dragons and swords.

Finally, we get the least prescriptive kind of cover, the most creative and sometimes, hardest to pin down. That's the literary novel (don't ask me to define it - I'm just talking about covers. I'm not paid enough to explain the contents).

Literary novel covers can be beautiful, strange and push the boundaries of what's possible in such a constrained space. Some of them are small works of art.

They repay a little more probing (like, you have to read the back and flick through the first pages to get a sense of the kind of story inside), follow fewer rules and come with more surprises.

In fact, even though they clearly belong to their particular end of the book spectrum, they actually do defy quick evaluation. Apart from knowing they fall under the large, umbrella-term of 'literary', you can't "judge them by their covers", and you can't guess whether you'll like them or not. The category is just too diverse.

Which brings me to human beings. I know, we're jumping all over the place, but bear with me.

I have a friend who is very quick to judge men. She thinks she can tell whether she'll be attracted to someone by just a brief meeting or a short conversation. Consequently, she makes a lot of mistakes.

She pursues relationships with men she finds superficially attractive and misses out on getting to know guys with whom she doesn't feel an immediate connection.

I'm not even talking about looks (or not only looks).

She thinks she's a good judge of character, but she mistakes character for personality.

Personality is something you can judge fairly quickly, but character takes a lot more time to puzzle out. You have to see the person in a variety of situations, watch how they react to sustained adversity, observe their attitudes to people and situations beyond the norm.

In fact, most of us have a tendency to see attractive personality traits and extrapolate positive character traits. Someone outgoing, confident and funny we're more likely to decide are honest, moral and kind.

In other words, we judge a book by it's cover. Which is fine for most books, but bad for human beings, who are more like literary novels than romances. They're complex, surprising and repay sustained attention.

Snap judgments are fine when it comes to things we buy. But let's take our time with each other, okay?