You should try Thrift Books they also offer inconsistency as a service.
I have ordered from Thriftbooks dozens of times. The only two things that happened was one package theft (obviously not their fault, but they re-sent the books for free, no questions asked), and one extra shipment of books I had not ordered (this was probably someone else's order that they sent me).
Ebay is where I get my out of circulation library books for really cheap. I just picked up a never loaned "Toward Artificial Sapience : Principles and Methods for Wise Systems" for $3.73. On Thriftbooks it's $156. Looking back, the seller was "BetterWorldBooks"!
Interesting... I've bought probably two dozen books from them over the past couple of years (via their Amazon storefront) and I've never had a problem with them.
I've ordered quite a few from them (novels, maths textbooks, ...) and never had an order cancelled. :-/
do they cancel your order or take forever to deliver?
Cancel order after about 4-5 days from experience. Had it on several books!
Order cancellations here as well, after books have been sent out and returned as undeliverable. Have not ever had that happen with any other shipment to my address, so I suspect they have a recurring issue with label printing. Their customer support just ignored me when I brought that up (several times) and issued a refund without any explanation.