Is it unethical for a professor to demand students buy their book then force autographing it before they can submit any work for the semester? I realize that it is really not unethical or illegal for a university professor to assign their own book that they have published as the textbook for a class. However, is it unethical for a professor to assign an expensive book, then require the students to get the book personally autograph to the student, by the professor prior to the professor accepting any work from the student? This creates several issues for me: 


Textbooks personally signed can not be sold back to bookstores. 
Used books can be sold to other students but when they reach the class, they are penalized for not getting their own book to meet the requirement of "personal autograph" to that student, which forces them to purchase the book again. 
Without getting the book signed, the professor will not accept work which results in a "0". 
The professor would not allow students to take pictures of notes in other students books but MUST PURCHASE the book, explaining "because you are not paying me". 
Essentially, this appears to be a "FOR PROFIT OF THE PROFESSOR" class. It isn't about the education of the student at all. 


I feel it is unethical. Do you? What should a student do about this?
Yes, some aspects of this are unethical. I'm surprised that a university would permit it to happen. They would, I hope, object if they learn of it. Especially if they learn of it from complaints to higher authorities. 

In my personal view as a professor and author, I can, certainly, assign one of my own books in a course I teach. But I believe that ethically, I should return to the student any royalty payment that I receive from the publisher. To avoid student cheating, I can purchase their receipt for the book from them so that they can't simply return it to be sold again as new. 

I think that the professor in question is trying to do something similar in part of this (autographing the book), but in an unethical way. 

I would think that autographed copies can be sold back to the bookstore, but not simply returned as new. Some autographed works are worth more, actually. The professor doesn't profit from the sale of used copies, of course. Only the "first sale" results in any royalties. 

I don't know how the professor "verifies" the purchase. Does he keep a list, or just ask to see an autographed copy? 

But, the issue of profiting from students when you require a purchase in such a way as to guarantee a profit is clearly a breach. As you describe it, it sounds like a clear form of coercion that should not occur and actually can pollute the relationship between student and professor. 

And obviously, most professor-authors think their own books are the best.