In order to create a book cover in Illustrator, you will first need to create a cover template in Illustrator. To do this, open the Illustrator file you wish to use as a cover, and click on the File menu item.
From the menu that appears, select the option to Create a New File. In the New File dialog box, select the Illustrator Cover Template option, and click on the OK button.
Once you have created the cover template, you will need to create the cover artwork. To do this, you will need to open the file containing the cover text and images. You can do this by clicking on the file name in the upper left corner of the Illustrator window, or by selecting the file and pressing the keyboard shortcut Ctrl+A (Command+A on the Mac).
Once you have opened the file, you will need to position the art on the cover template. You can do this by using the guidelines that appear when you click on the Artboard button in the upper left corner of the Illustrator window.
Once you have placed the art on the cover template, you will need to make sure that the artwork is correctly sized. You can do this by using the sizing guides that appear when you click on the Artboard button.
You can also use the rulers that appear when you click on the View button.
Once you have sized the artwork, you will need to make sure that the colors are correct. You can do this by using the Color Picker tool that is located in the Tools panel.
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You can also use the Eyedropper tool to sample colors from the artwork. Once you have selected the colors that you want to use, you will need to click on the OK button to close the Color Picker tool.
Once you have selected the colors, you will need to make sure that the shadows and highlights are correct. You can do this by using the Shadow and Highlights tools that are located in the Tools panel.
You can also use the Blending Modes tool to change the blending mode of the shadows and highlights.
Once you have made the adjustments to the colors and shadows and highlights, you will need to click on the OK button to close the Illustrator Cover Template dialog box.
Once you have created the cover template and cover artwork, you will need to save the file. You can do this by selecting the File menu item, and selecting the option to Save As.
In the Save As dialog box, you will need to enter the filename of the file, and click on the OK button.
Once you have saved the file, you will need to close the Illustrator file. You can do this by selecting the File menu item, and selecting the option to Close File.