I’d have a couple minor comments about your beer tree however. Mild isn’t it’s own style of beer. There are british pale ales (mild, bitter, esb). also there are american and british brown ales, the latter of which can be grouped into mild, southern, northern. Also I don’t see the red/amber german lagers of Munich style (oktoberfest, etc.,)

Check out http://www.bjcp.org for the official competition handbook on styles. Also Brewing classic styles by Jamil Zanichef(sp?) is a fairly comprehensive book. Both of those are geared towards homebrewers.