Less than a dozen.
The majority of customers at the museum aren't train enthusiasts, let alone model railroaders. One visit to the gift shop, and it's pretty easy to see. Junky train toys, and Thomas toys.
It's been several years, but my own experience was that they had an excellent selection of books in the gift shop, especially on midwestern railroads. My wife (I don't know how she did this while I wasn't looking) picked up a Christmas present for me while we were there (she saw me paging through it)- Ed De Rouin's book on the C&EI showed up under the tree.
And yes, I am sure you are correct on most visitors not being model railroaders. Although "aren't train enthusiasts" seems a presumption. Why pay admission if you don't like trains? There are lots of other things to do that require less driving from Chicago. Do you have a chip on your shoulder or just a critic of gift shops?
Not that I really care about gift shops. They have an excellent collection of railroad equipment. And they seem amenable to those of us who travel around with cameras (I know, old fashioned of me) and tape measures. Plus we can ride around on trolleys and such.
