GPG vs OGP

Nice subject, isn’t it?
Ok, I’ll make it clear :
Game Programming Gems Vs OpenGL Game Programming.
Which of this two books do you suggest.
I’ve heard good opinions about both of them but I if buy them all I won’t read them (it would be too much for a one time ). Which is better, or which one should I read first. What I like to know are some algorythms used in games programming presented in OGL. DirectX is also well welcome.

Thanks for any advice!

Orzech