But costs a lot of money, especially just to do a sample cover.
One thing we forgot here (multiple personaly disorders to that a lot) is that GIMP also comes in a "GimpShop" configuration to emulate PhotoShop interface.
But really, Paint.net is your best bet: free, good support forum, extremely instinctive and easy to use. It can take HOURS to figure out how to do things on Photoshop. Many of the things you see big online PS tutorials on can be done quickly and easily on Paint.net. Use of layers and transparency is not an esoteric mystery there: it falls easily to hand. Rotation is handled with an ingenious single control that allows zoom, rotation and 3-D "tipping" all in one simple box. It allows use of hexidecimal color codes instead of the onerous RGB type-in.
The control over flooding color in with the "bucket" is a simple slider and it doesn't get all weird with half-colors that you have to look up and figure out.
It's not as heavy into cool brushes and stuff, but you probably aren't going to be creating art, just assembling it.
A really good piece of free software and an EXCELLENT introduction to using graphics programs.
Our designer used it for the sig banner below and almost all of the design work on the site it clicks to.
GIMP really shines when it comes to creating logos, titles and type. You can just type out your title, name, etc then use the Alpha-Logo filter to turn them into an impressive array of neat graphics with no background knowledge required.