This book does a good job of introducing the readers to the basics of computer vision - it really has nothing to do with robots outside of the last chapter, other than if you build one and need to give it vision capabilities, you need to know the information in this book. Physics equations via calculus and ODE are used to describe how light intereacts with solid objects and also with image sensors, the latter tieing in to the subject of robot vision. Therefore, the reader should have a good knowledge of first-year university physics as well as multi-variable calculus. As a reference for the geometrical and physical mathematics of light interacting with surfaces and the camera, it is particularly excellent.
Horn does a great job of deriving and providing the equations you need, and brings it all together with excellent narrative and very good illustrations. The book goes all the way from the basics of image formation, to simple matrix operations such as edge detection, to some more advanced topics such as shape from shading. The final chapter, on picking parts out of a bin, uses the ideas developed in previous chapters to come up with the basic design of a robot hand-eye system that is capable of picking up specific parts from a parts bin. It really is a very good unifying capstone to the entire book. The only drawback I can see in the book is that it pretty much stays in the domain of continuous mathematics. There is not much in the way of explicit algorithm steps - the author expects the reader to be able to do that based on his explanation and equations, and given the high quality of the text this is really not too rash of an assumption.
Because of its age it doesn't have some of the more modern techniques and algorithms, but if I had to choose between this older book and that more recently published waste of trees, "Computer Vision: A Modern Approach", give me this book every time. You get a firm foundation in the basics, plus a good understanding of some more advanced topics too.