If you are laying out images of spreads or pages or brochures somewhere like in portfolio, consider this dimensional effect that will make your work pop out of page and instead of plain static images you will have dynamic effect that will bring more interest to your work.
Step 1: Create a layer. With Rectangular Marquee Tool (command+m) make a selection. Inside the selection with a Gradient Tool (command+g) make a gradient (see step 1 image)
Step 2: Duplicate the layer with gradient (command+j). Then transform it horizontally (command+t, right click+horizontally). Move to the other side where first page of a spread ends. You can also make its opacity stronger about 20%.
Step 3: Follow the first step only create a white gradient (see details in the 3rd step image). After making the gradient you can narrow it down a little on the bottom of the image with an erase tool (command+e). So, on to the white gradient would be wider and on bottom narrower.
Step 4: Duplicate the white gradient layer and move it to the right side. This will give a feel that the page is bended up just a little (see image for details)
Step 5: This step isn’t necessary, yet you still can do it. I just duplicated a white gradient layer again and converted color t black (command+i). Then moved it aside and lowered its opacity just a little. This gives it even better feel of dimension of the piece.