My suggestion? Don't buy them. Complete the ones you have, study them, then get vol.3, finish it, then vol.4, then 5.
Getting the whole collection in a snap will just make you bored, when you see all the material, you'll jump from the pass to color changes ....etc.
The books wont go out of print for quite some time. So study the ones you have, and complete the collection later. Yes, the books are the best for card magic, finishing them and applying the moves as Roberto, the author, teach you will make you better than 90% of today's magicians. ( the author said something along these lines in his introduction in vol.1, read it ).
~ Feras