^ what melvan said.
it also depends how serious you are / how much time and energy you're willing to commit. (although i guess if you're planning on organic you're pretty damn committed, right?) (<--you should be.)
greg green's grow bible, IMO, is much more comprehensive than jorge cervantes' (<--a brilliant writer with loads of good information, he just has this pesky habit of contradicting himself a few chapters over which i find most aggravating. not to mention he needs a new publisher. the last 3 editions were rife with typos and missing half-sentences)
one of cervantes' books you might want to get a hold of is 'marijuana indoors: 5 easy gardens'. if the guidebooks cover theory (from my experience with novice growers, this can result in a "so now what?"-type of quandary), this is 5 case studies of what actually works, including one from the original breeder of the strain 'romulan'.
just one more thing: you want to do good research on the nute system you end up using, think it through really well and make sure it's going to work for YOU specifically. i mention this because i've heard seriously mixed reviews about
fox farm: it's like the brussels sprouts of nutes: the people who like it LOVE it, and the people who hate it want to firebomb the factory it comes from.