I guess it depends on what you need to study... For me, I had no way of knowing I already had all the info I needed with the books I already had for the tests I need (NC 1-6), so it was just a waste...
Another good one is the Lippincott RN NCLEX, and you can buy them new at the Lippincott website for about $40, they also have the Incredibly Easy Series for about $40 as well. I bought Chancellor's...
I made the mistake of buying the guides from Chancellor's - another publishing company. Before it was said and done I owed them over $3000, not including the money I still had to pay Excelsior for...