The WVC Bookstore (509-682-6532) should be your first stop, as it should always have a copy of the required text on hand. It also often has used copies or copies for rental.
WVC Libraries maintain copies of many course texts behind the Circulation Desk. You can browse or search them by using the Course Reserves section of the catalog. Note that course reserves can only be checked out for two hours at a time, and may not leave the Library.
Another option, especially for older works, is to run a search of E-Books in the library database collection.
Amazon has its own textbooks store. In it, you can find new, used, rental, or E-Book copies of your required reading. Pair that with an Amazon Prime Student account and you can get physical books shipped to you within two days for free. Other potential stores for physical or digital textbooks are Chegg, Textbooks.com, Half.com, AbeBooks, and Barnes & Noble. It may also be worth trying the publisher’s web site if these other options yield no good results.