Here Comes the Shaggedy (Goosebumps Most Wanted)

The infamous, Most Wanted Goosebumps characters are out on the loose and after you..
Kelli and Shawn Anderson are not excited about having to move to another state - especially because their new home is directly next to a giant swamp. But their dad is a scientist and he's going down there to study the local flora and fauna.
Unfortunately for Kelli and Shawn, there seem to be some very strange creatures that live around their house. They keep hearing about the legend of the Shaggedy, an ancient beast that lives far below the surface of the swamp and can cause a whole lot of damage. Can Kelli and Shawn convince their dad to move back home before it is too late?"

R.L. Stine has more than 350 million English language books in print, plus international editions in 32 languages, making him one of the most popular children's authors in history. Besides Goosebumps, R.L. Stine has written other series including Fear Street, Rotten School, Mostly Ghostly, The Nightmare Room, and Dangerous Girls. R.L. Stine lives in New York with his wife, Jane, and his King Charles spaniel, Minnie. www.RLStine.com.