Wow this is an old thread but what you find out there is a mix of GM licensed and boot-legged reprints.
I bought my first AIM at a swap meet back in 1982. It is loose leaf bound with plastic binder. I was an obvious Xerox copy of an original and it is printed on green paper. While it was bound with a plastic binder spine, the pages and the cover were also 3 hole punched so you could take it apart and stick it in a standard notebook binder. It was 25 bucks.
I bought another swap meet one that was professionally bound like a real book but again the quality is bad on some pages but different ones then the first. This AIM has a green cover (same picture as the other one I already had) and is printed - again a Xerox copy - on white paper. Item number MP74 for $19.95 since the hand written price tag is still on the cover.
While I had a boot-legged copy on PDF that someone gave me, I wanted a legal digital copy and ordered the official copy from Dave Graham Auto Literature. I ordered 1969, but the disc has all three years, and at the time I placed my order they included a free copy of the printed 1969 AIM version so it was a win win win for me and it was cheap. $22.99 plus shipping from their 800 number. Still on-sale through their website and Amazon. http://davegrahamauto.com/
Word to the wise the catalog is HUGH and takes 5 to 10 minutes to download, but you can call them for what you want.
Why keep 4 printed copies? Well I keep one in the garage, one in the library, one at my desk and a spare in my room. I use the PDF a lot to snap pages to JPEGS for posting over at Team Camaro as the legal digital version has too many security hoops to jump through to get a copy of a page made. I guess the answer is to say I use all my copies to find hopefully one that has a clear copy of whatever page I'm trying to use. Out of my collection the legal printed and digital copy are the cleanest print wise but still some of the change logs at the bottom are hard to make out.