textbooksrus.com textbooks R us Company gives your prices to buy your textbooks, once you sign up, they claim they are not buying those same books. Nationwide

If they were no longer buying the books, they shouldn't have quoted prices at which they would buy them. It doesn't make sense for them to offer a price, collect your personal information and then refuse to honor the price quote.

If they aren't buying those particular books, they should say so up front rather than offering a price for them by ISBN number search, no less.

It would appear at least the site is legit. As far as phishing I don't necessarily think so. Could be just bad info was given to you by someone who may have had wrong information from their management or something.

I am not sure if it will help you or not but here is the info from ARIN.net


Name
UBX Book Exchange

Handle
C00806091

Street
2340 Wood Ave.


City
Columbus

State/Province
OH

Postal Code
43221

Country
US

Registration Date
2004-04-19

Last Updated
2011-03-19

to sell the books locally,bookstores, ebay, or craisgslist.

If that was the reason, I would have not been upset.  This company offered me a certain amounts for each of the books before I signed up with my membership.  They claimed that they were accepting all these books for which I inquired about with the ISBN numbers.  It was not until minutes later, after they got my personal info that they decided that they are not going to accept these books.  What they did is illegal according to the AG's office. 

It is very possible that they decided not to buy the books because they were no longer being used for the classes that you bought the books for to begin with.

Everyone that has attended college knows that the books the teachers use are changing all the time.

Why buy a book from you when they will not be able to resell it? Maybe just bad timing on your part since the Fall semesters are starting up this month and the colleges have selected the books that they will be using for this term already.