Ebook: Agile Management for Software Engineering: Applying the Theory of Constraints for Business Results

I don't mind buying books from Amazon, but the only thing about Amazon is they charge you shipping charges, why can't they just ship all the books at one time instead if they are in stock! I know it is only a estimate but we put the estimate on the purchase orders, and when we receive each item, there is a charge for each shipment! When we have to reconcile the orders, the amount is different then what is on the purchase order. So we have to do an amendment to either increase or decrease the order!
Also if the books are instock at the time I order, why do they send messages saying "Your order is delayed and will be shipped at a later date, what is up with that if they are in stock! Ordering from Amazon is a pain!