This is a simple guide for making a 3D book cover in Photoshop. This can be used to modify your flat 2D book cover to make it look more professional. In order to do it in Photoshop, you will need artwork like this one:
You will also need a 3D book cover template, like the one below.
Once you have that, you can open the template in Photoshop. It should look like this:
Once you have the template loaded to Photoshop, you can load the book cover artwork on top of that. Make sure you have exactly two layers and the artwork layer is above the template one:
Now you need to align the artwork with the template using the Edit → Transform → Distort tool. Drag the artwork corners so they match the front part of the 3D book template.
Once done, press Enter to confirm the changes. The artwork should look like on the actual 3D book cover.
Finally, you can add shadows by setting the artwork layer type to Multiply so the artwork catches the shadow gradient of the template:
Done, the 3D book cover is ready! You can automate this process with actions to make it go faster if you are regularly making 3D book covers with Photoshop.
Since using Photoshop involves the use of templates, it does run the risk of making your 3D book cover look generic. Using special software may give your 3D book cover a better look.