This is, as others have stated, an issue with the shipping company and not the retailer. Perhaps, given the accounts posted here, the retailer should consider posting a note on their shipping page alerting the buyer to the possability of delays. I would completely expect a deep discounter to use the most affordable method of shipping possible as their default (or only) shipping method. It preserves the discount. Perhaps they should look into additional shipping options, although they may feel they are doing enough business without the hassle of dealing with additional carriers.
If you can't wait for the books, try another retailer. I buy pretty much exclusively from Amazon. The books are almost always discounted and, even though sites like buy.com offer deeper discounts, Amazon usually has the best price once shipping is figured in. And the free shipping option still usually gets to my door on the 2nd day after I get the shipping confirmation.