[BNM] SEO book?

[Rich 1985]

Evening folks,

I have a basic grasp of SEO and code generally to a good CSS/W3C 
complaint HTML standard, with sites that have quite a lot of written 
content, but I'm looking to extend my personal knowledge of SEO to a 
more advanced level... hopefully in order to get some better organic 
results for a few corporate clients.

I'm seeking as up to date a resource as possible and was wondering if 
anyone can recommend a good book or online resource / blog that I could 
wade through over the coming weeks?

Any recommendations would be much appreciated.

Regards,
Rich