What makes more money an eBook or affiliate marketing / Google Adsense

Hi

I’m interested in trying to earn a little extra cash either writing a short eBook to sell at around £1.99 about fitness training or build a site with adsense links on there which has content relating to fitness training. Has either of these options actually made anyone money and if so can you give me a rough indictaion of what ballpark I should be looking at making. Can anyoen suggest which route I should try first?

Many thanks