I wouldn't call myself a market gardener. I do have my own garden, and I do work on a relatively large (per volunteer) community garden, but I'm by no means a professional. It is in my future plans though, which is why I like to read up on issues surrounding sustainable agriculture.
I also think the second edition of Building Soils for Better Crops is particularly relevant to this forum.
SARE's publications are nice because they're reasonably up to date, and relavent to agricultural operations that are larger than personal gardens.
Anyways, I could list a lot more publications on agriculture that I've found interesting, but those are two of my favourites that are a lot less well known than Eliot Coleman's books.
Feel free to chime in with your own recommendations.