There are now copies of the Boyer, Borstelmann, Vonnegut, and Zaretsky books at the bookstore, according to their website.
There are also two copies of the Boyer book on reserve at the library, now, as well as the two monographs.
Just checked the bookstore website, and it appears they have used copies of the Boyer textbook in stock, and for less than you might spend online. Check it out.
Other confusion? Have an idea or some inside info on the required books? Comment away!