@jo

A View Master

The original View Master

A Reel

Oh, Thooose were the view masters you talking about?  

They required no batteries and were simple for even a fairly young child to use. One just moved a small handle manually on the side and this would move the reel on to the next photo. We would get lost in story-telling via those little treasures.

Yes, but with whom? Yes, I remember those circular slides, but those I did vaguely remember coming in contact with, were random pictures or tourist-type pictures. I never knew they could be associated with stories I read, like Heidi, as @narnian78 mentioned. I'd forgotten even the name of the gizmo on the links you provided, that ran them.  

@waggawerewolf27 

Some of the reels like Heidi had real people in them, but others like A Christmas Carol and 20,000 Leagues Under the Sea had people that were artificially created so that they looked appealing to a child.  I guess the creators of the reels thought that the artificial characters worked well enough to tell the story. The pictures were three dimensional so that you could see depth in them, which made them better than most cartoons. The pictures of the national parks and wildlife were actually of real places and wild animals.