Slime That Ate Crestview, The (Vintage Paperback) by Jahnna N. Malcolm

They've been slimed! 

What could be more excellent? It's the middle of summer, and there are no parents around during the day. Maddy, Keegan, and Einstein rule their brand-new neighborhood. 

But then, just as they're getting bored with TV and their skateboards, all three realize that something's not quite right with Crestview Estates. Pets are disappearing. Construction sites are sinking into the ground. And a purple slime is surfacing... 

It's ooey, gooey, and after them! And nothing's going to get in the way of this slimy sucker.