We are always told not to judge a book by its cover. Yet book covers are so influential on the way we perceive the text inside them. In order to pick up and read an unknown book there has to be something curious or alluring about its cover. Book covers are produced to be colourful and eye catching, to be unusual and genre determined. A good book cover is one which is striking, timeless and memorable.

It is arguable that many people associate their favourite reads with the cover of the edition that they first read it. They are irrationally biased towards that cover regardless of the different re-issues that the book may have had. Although the cover might not be a piece of innovative illustration or design they are emotionally attached to it because of its association with when they first discovered this book. They would argue that it is a good book cover.

Book cover art is almost a forgotten form. With the increase of digital technology most book covers seem to be a mesh of photo images manipulated by computer graphics. These can produce pleasant but forgettable covers. Yet some publishing houses seem determined to utilise technology to produce covers that are innovative and memorable. The bold, graphics of Penguin covers is still a legacy that continues today through manipulation of technology. The iconic graphic cover of Anthony Burgess' A Clockwork Orange has been replaced in the Penguin Modern Classics series by a cover that is just a photo of a glass of milk. In its own way this cover is just as arresting and exciting as the original.

Books covers do not always have to be plastered by pictures. Faber & Faber's poetry series make a very striking and collectible set of books despite there being no illustrations or graphics. This sentiment almost echoes the original Penguin issues where the only way to distinguish one book from the other from appearance was the title.

What makes a good book cover is the quality of the design. Some covers are designed to sell and appeal in the short term but the ones which have most impact are the one that define and enhance the book inside.