Reddit reviews Experiences of Test Automation: Case Studies of Software Test Automation

I would start with just reading random blogs and articles that you can find. This is pretty good but might be a bit advanced abstract if you have no hands-on experience: http://www.satisfice.com/articles/cdt-automation.pdf

Also note that different roles mean different things when they say "test automation". Often you cannot really tell whether people mean unit testing, api/integration testing or GUI automation when reading an article.

In case you are looking to implement some for of automation in your team/company, this might be a must read:
http://www.amazon.com/Experiences-Test-Automation-Studies-Software/dp/0321754069/