On Origin? Together they're both $50 on Origin, you must have some awesome coupon.
Don't know if anyone else does this or if it's just me, but if I buy a sequel to a game then I'd have to buy the previous titles as well. It's kind of like starting a book series on the 3rd book or something.
I just read the wiki article on the previous one, although the game usually fills you in anyway.
The only exception was I jumped right into Mass Effect 2 without beating the 1st and I was so lost on the story until I read the wiki.
Also I used the coupon from OP to get Mass Effect, Dead Space, Spore and Spore Creepy and Cute for free, it was quite an awesome coupon haha