Its a lot of cards to be missing from the deck - if you've bought it new, then really you should consider taking it back, its faulty and they will replace it. If you've bought it online then get in touch with them first sometimes they will just send a replacement out.
Is it the Golden? Have you gone through the deck properly because with the gilt edges sometimes cards stick together and need a little help coming unstuck. You won't have to do it again, just the first time. I'm sure I had a similar experience with my golden, and found the missing cards stuck together. It just seems like an awful lot of cards to be missing.