What is a book? Research - Front cover

Firstly I have looked at different dream dictionary book's covers to get some ideas and inspiration from them. First of the book's which I have found is 'The illustrated dream dictionary' by Russell Grant. I really like the front cover of this book as it is containing lots of interesting and limited colours illustrations. I would love to use my own illustrations for the front cover. The illustrations are very simple yet powerful. You can tell what the book is about without reading the title. The colours perfectly suit the theme as blue, white and yellow contrast well witch each other.

As I want to include illustrations for my front cover, the other example which I have found is illustrated 'Dream Dictionary & Record Book' by Pamela Ball. The front cover contains lots of colourful line drawings. Yon can clearly say what's the book is about without reading the title because of the yellow illustrations of stars and moon. Also the blue background which symbolise the sky. 

The other example which I have found is 'The bedside dream dictionary' by Silvana Amar. Looking at  this front cover first thing which catches my eye is the word 'Dream' in large, bold font in white colour. The cover use an image of the clouds and moon. Blue and white colours perfectly suit the theme. 

Looking at those front covers I have realised that all of them are using illustrations of images of the moons, starts and clouds. Most of them uses limited colours such as blue, yellow and white. I will try to design my cover in a very simple way, using simple, yet powerful illustrations. I want to make readers know straight away what the book is about without looking at the title. Moreover I need to think of the title or slogan for my book which will catch readers attention to it.