All the heads are basically the same. They are worked in the round. The head hangs outside the book and helps the reader find their place easily.
Here are some tips that I have found for adding sculpture to crochet heads. Most sculpture crochet patterns create the sculpture with the stitches as these patterns do, but to add a little more depth and height to the sculpture there are a few things that can be done.
I am not an expert on embroidery but I know some of the basic stitches. I use simple straight stitches for the eyes as this give me the look I want, although I am sure a French knot would work for more rounded or dot eyes such as the Raggedy Ann and Andy Patterns.
Since the nose should be higher than the rest of the face, the nose needs to be built up. Using the skin color, I again make a hidden knot by going in through the back and pulling the knot through to just below the surface. Bringing the needle out the front to a point exactly in between the two eyes, I do a series of straight stitches from between the eyes down to a row above the mouth. Again, I bring the needle to the same point between the eyes and fan out the stitches at the bottom of the nose. I continue to build on top of these with straight stitches until I have a large enough nose for the face.
The lips are again simple straight stitches. I found that trying to do a smile just makes the piece look silly so I do a single straight stitch on the row below the nose and two smaller straight stitches just above this.
I hope this helps explain some of the techniques I have found in making simple faces on small crochet pieces such as the bookmarks.