yes - you download books when you are at a wifi place (some use libraries, some starbucks)
once you have the downloaded they are on your kindle till you tell it to "remove from device" The books are still part of your archive - you can access your archive - but to download you need to be using wifi
I only have wifi, my mom has the 3G - I dont think she uses it, I thought she might need it for when she travels.
The $79 does not have a keyboard -the only thing I use the keyboard for is making "collections" I have collections like Fiction, non fiction, bestsellers, currently reading etc - then I put the books I have downloaded into those collections... BUT you will have the ability, without a keyboard, like the old phones and texting to type words
my dd uses her keyboard all the time - she buys books (free or cheap$.99) with her kindle - I use the computer - she has free games that she uses the keyboard for - I dont have games, I like reading.
The special offers is when your kindle is sleeping (its reccommended to let it go to sleep dont turn it off - it goes to sleep after a period of time - on my kindle I have images that area stored, and rotate - affectionately referred to as "dead authors" Jane Austin, etc - some find those "creepy" But when I start to read, I no longer see them
Special offers is "ads" from
Amazon - you only see them when your kindle is sleeping - I highly recommend getting a case for your kindle - close the case, you dont see the authors, or offers
some have reported that the authors can be a "good deal" (gift cards is the one I remember reading about)
Good Luck!
we love our plain kindles!!