For non-mathematicians the way to understand the shape of a wormhole is to start in two dimensions where we can represent space by a flat sheet. A wormhole is where two parallel sheets are joined together. This diagram (attempts!) to show how the wormhole joins the two sheets:

Start with the two sheets representing the two different regions of spacetime, then punch out a circular hole in both. Now bring the two sheets together and glue them along the edges of the holes. The bottom diagram is supposed to represent the two sheets brought together and glued along the edges of the circle.

When you've done this, you can start on the upper (blue) sheet, travel towards the wormhole and when you reach it you'll go though it and find yourself moving away from the wormhole on the lower (red) sheet. Incidentally, if you start in the blue sheet and look towards the wormhole you'll see light from the red sheet that has travelled towards the wormhole, through it onto the blue sheet, then away from the wormhole towards your eye. That's why Brian says the wormhole will look a bit like a mirror.

Anyhow, the point is that to a Flatlander living on either sheet the wormhole looks like a circle. If you now replace the 2-D sheets by 3-D spaces you join them in a similar way but this time by cutting out a sphere in each and joining them along the surface of the sphere. That's why the wormhole will look like a sphere. Sadly my drawing skills aren't up to drawing the 3-D diagram.

Actually the wormhole can be any 3-D shape. See https://physics.stackexchange.com/questions/69521/negative-energy-and-wormholes/69539#69539 for how to make a wormhole in the shape of a cube. You could make the wormhole an arbitrarily thin disk, subject only to your generating system being able to generate enough curvature at the edge of the disk. This would resemble the conventional circular portal.

All very well, but what Brian actually asked was if any authors had treated wormholes properly in their books, and the answer is that yes, of course, many have done so. For example in Axiomatic by Greg Egan and Cosm by Gregory Benford and doubtless lots of others. Gregory Benford actually references Matt Visser, who wrote a non-non-nerds guide to wormholes back in 1989.