Definitely need to buy the Unit Reader. (Really well written, too). Practical Ethics by Peter Singer is also a compulsory textbook and you definitely need to read some of it to get the marks on the ATs. I suppose you could borrow it from a library every time an AT comes around and prior to the exam, and only do the readings required for the various ATs - however, this will leave you with an extremely stunted and shallow understanding of the course material. I really would just buy Practical Ethics (very interesting read, anyway!). These two are all you will ever require.