Any Good Books On Advanced PPC Optimization?

[ppcads]

Hey everyone,

I've been in the PPC business for a while and have a very good grasp of the basic and some good advanced techniques but the last month or so I feel like I havent learned anything new. I see the same old "tips" and as you guys know, Google and Overture are not very helpful either.

I learned as I went and was able to get squeeze out info from my reps at the search engines, but I need more info and I am willing to pay for it.

Can anyone recommend any good books, online or offline that go past "High CTR * High Max Bids = placement" and not to bid #1 on overture and blah blah blah?

Thanks for your help

[eWhisper]

Overture has a nice free tool:
[webmasterworld.com...]

Google's Maxium Effect PDF:
[webmasterworld.com...]