Before we get into the books I am going to talk about the activity. If you look online there are a gazillion recipes for goo, slime, ooze, playdough, puffy paint, etc. but I am going to give you my favorite one to do (which also happens to be the easiest). There are only 2 ingredients: cornstarch and water. You do not need exact measurements; just pour some cornstarch in a bowl and add water until it looks liquid but feels solid when you give it a quick tap on the surface. As you can see from the picture it looks like a bowl of milk (unless you add food coloring).
Now for the fun stuff. Scoop up some of the goo into your hand and try rolling it into a ball. If you move your hands quickly you can do this. Stop moving your hands and hold them out, palms up. The goo should look like ice cream melting. It is fun to play with even when you are an adult, right?
This video gives the scientific explanation for why the cornstarch and water mixture feels like a solid, but can also flow like a liquid. If I had the money to go out and buy a couple hundred boxes of cornstarch I would totally fill up a giant vat so I could run across it!
Slime also goes perfectly with any of the Black Lagoon books by Mike Thaler. Of course, my personal favorite is The Librarian from the Black Lagoon.