[RE-edit] They changed the T&C's to exclude popular penguins :(
If you can find a $20 book then this is 50% off!
Good luck with that…but you can get some paperbacks for under $25 so it's still a respectable 40% off and a reasonable price for a book you can get hold of immediately.
The DVDs - I doubt would be cheap even with $10 off, if they even have any decent DVDs left after the recent sales.
Penguin books are $10