The best site to buy textbooks is Amazon.com.  I have been doing it there for several years with great success. Other sites have goofed me up by reporting that the book is on back order or not available for a several weeks. Amazon sellers have always shipped very promptly. One time I got the wrong book, and Amazon supported me getting a refund. Looking at a seller’s feedback can give you a warm fuzzy feeling that you are dealing with a known seller. I have been able to buy books well under the local university price, and also sell my used books for more than what the bookstore will give me for trade. My second favorite site is Ecampus.com They have always been very prompt in shipping too.