If application of force does not result in spatial movement, has work been done?
No. No work would be done in this case, at least not at the macroscopic level. Work is the product of force and displacement in the direction of the force and in this case there is no displacement.
I disagree with you that each person is "accomplishing a change in the book's movement". The book wasn't moving initially, or at the end, or at any time in between. The situation is exactly the same as if two people had been trying to push the book through a solid wall.
Be careful when using the human body in questions where you are asking how much work has been done. If you actually try what you propose you will find that you will get tired. Your muscles are losing chemical potential energy but you are not doing work on the book. At the microscopic level your muscle fibers are contracting and slipping and contracting again so at that level work is being done.
I find it more instructive to think of replacing the people in examples like these with some sort of simple mechanical device. You could lean something up against the book, use a clamp or set up some other simple mechanical system which would continue to apply a force but would require no ongoing energy input, which makes it clearer that no work is being done.
Their lesson today says that "work" is done only when a change in position is accomplished by application of force.
The key word here is change. If an object is not moving, then no work is being done to it$^*$. Therefore in your scenario, no work is done on the book by any of the forces acting on it.
More formally, work done by a constant force on an object moving in the direction of the force is given by $$W=F\Delta x$$ where $W$ is the work done by the force $F$ over the distance $\Delta x$. If the force is at some angle relative to the direction the object is moving, but the force is still constant and the object is moving in one direction, then we pick out the component of the force that is along the direction the object is traveling: $$W=(F\cos\theta)\Delta x$$ which has a shorthand notation for vectors $$W=\mathbf F\cdot\Delta\mathbf x$$ If we have more complicated scenarios of forces that are not constant and objects whose directions are changing, we just "zoom in" onto the path until we have small segments where the force is constant and the object moves in one direction. We find the work $\text dW$ along this little part of the path $\text d\mathbf x$ as before then: $$\text dW=\mathbf F\cdot\text d\mathbf x$$ and then we just add all of those little works up. Welcome to calculus:$$W=\int\mathbf F\cdot\text d\mathbf x$$ The $\int$ symbol qualitatively means "add up all of these little values."
Going back to your book example, there is no path the book is moving on. $\Delta x=0$, so $W=0$.
Since each person is accomplishing a change in the book's movement (stopping it from moving) would that not be considered work?
No. First, "change in movement" is not the same thing as "change in position". Second, the book is remaining stationary, so nothing about it is changing. Work doesn't take into account the idea that "well if this other force was gone then the object would do this instead". You just focus on what is happening, not what could be happening due to some other scenario.
$^*$Technically we are interested in the point of application of the force. But for non-rotating rigid bodies the distance covered by the point of application is the same as the distance covered by the object, so we can often use these two interchangeably.
It's complicated.
The simple idea for simple situations is to think of it as force times distance. And that does work.
In thermodynamics, work performed by a system is energy transferred by the system to its surroundings, by a mechanism through which the system can spontaneously exert macroscopic forces on its surroundings, where those forces, and their external effects, can be measured. In the surroundings, through suitable passive linkages, the whole of the work done by such forces can lift a weight.
Wikipedia
So any energy transfer is work if it could possibly be converted into moving a mass.
Say you push electric current through a resistor. At first sight, all that moves is the electrons. But heat is produced. The heat is partly molecules vibrating faster, and partly it is radiation that could someday cause other molecules to move. All that movement and potential movement is work. Because energy has been transferred.