Any opinions on this opening? I don't play Ruy Lopez as white, do you like getting this against you? Favorite lines?

I've been taking a liking of this defence from black's point of view. Does anyone know of any good books which have this variation as a main theme?

Mr Gorbechev, tear down this wall.

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Ah, don't we all wish our opponents would just tear down their walls :(.

I think this is the Berlin Defence to the Ruy, and the Berlin Wall proper is the subvariation that arises after 4.0-0 Nxe4 5.d4 Nd6 6.Bxc6 dxc6 7.dxe5 Nf5.

The tough part is that it looks like White ought to be a bit better, but it's just completely unclear what White's plan is supposed to be.

John Cox's The Berlin Wall: The Variation That Brought Down Kasparov is supposed to be a classic opening book that I've even seen recommended to people who don't play it.