I just purchased this .EPS blank book cover, I thought I'd get it in .psd format, but I got it as a .EPS format, and I have no idea how to integrate the cover of a book in it.
Since you already have the file, you can drop your cover art into it using Illustrator.
We're going to use the front cover shape as a clipping mask for your cover artwork.
Import your artwork and move the layer so it's just above the front cover shape.
Duplicate the cover path and place it above the cover art layer.
You'll need to distort your artwork to match the perspective and curve of the cover. If your art is vector, you can use various Illustrator tools until you get it right. My sample has a raster image in it, so I distorted it in Photoshop and re-imported.
Select your cover art and the duplicate cover shape and Make Clipping Mask (Object > Clipping Mask > Make). Set the clipping group to Multiply so it picks up the shading of the underlying shape. Your art can either extend to the spine area, or you can place separate spine artwork in that same clipping group.