I used half.com all the way through college (ISBN makes it quick), but it would be much easier if the chosen textbooks were announced earlier (like you point out). Most of the time I was without a book for the first week to 10 days.
The lead time issue could be fixed simply by changing University policy, requiring professors to disclose required textbooks X weeks in advance of the first day of class.
One loophole I found near the end of undergrad was that the campus bookstore's website had the required books posted for each class well over a month ahead of time (so you could buy them online and swing by to pick them up). I just looked up all my classes there, copied down the ISBNs and hit up half.com or Amazon. Of course, this breaks down with last minute changes or additions made by professors.
The lead time issue could be fixed simply by changing University policy, requiring professors to disclose required textbooks X weeks in advance of the first day of class.
One loophole I found near the end of undergrad was that the campus bookstore's website had the required books posted for each class well over a month ahead of time (so you could buy them online and swing by to pick them up). I just looked up all my classes there, copied down the ISBNs and hit up half.com or Amazon. Of course, this breaks down with last minute changes or additions made by professors.