So, I found this "board" game (appears its a spin off of the D&D table top book games) at the local church sale they were having in my town here, and wanted to know more about it. 

So, what i want to know, Is this set supposed to have more books with it? Or is it individual copies purchased separatly and stored in this box, similar to how board game sets nowadays include room in the core set for expansion packs? 

All the books included here have their respective maps included as well.

Any information would be helpful. Thanks! 

Gamma world is a series, there's hundreds of gamma world items. That box is the first edition set, and looks like two extra adventure modules added.

Edit: One if famine in Far-go, the other one not sure on, not a big gamma world fan.
Edit #2: Oh wait that other ones easy, it's GW1, Legion of Gold

These were the only two first edition modules, and the only other 1st edition item I know of is thereferee's screen, so find one of thoese and you have a complete line of 1st edition stuff.  Why, that would be worth tens of dollars. First edition was 1978-1983

Edit #3: Apperently gamma world wasn't as big as I thought, while it had 7 editions, they didnt release much in any of them.  I may have to start picking them up at half-priced when I see them cheap.

Gamma world is loads of fun, especially in the earlier editions. I need to start picking up some of them soon myself.

Gamma World is actually a "role playing game" in the style of Dungeons & Dragons, as opposed to a "board game" (and is awesome). It did not come with miniatures, cards or other traditional "board game bits".

The box, map and b&w booklet you have make up most of the original "core set". As best I recall, you're only missing the original dice and character sheets (both of which are easy enough to replace if you intend to play it).

As Ozzy mentioned, the other two booklets are the first two adventure modules, which were sold separately.