Check out You've Got Dragons by Kathryn Cave.
Harry and the Terrible Whatzit by Dick Gackenbach.
In this treasure, Harry has an unfounded fear of the unknown in the basement based on what he knows: "It was dark, and it was damp, and it smelled." I found humor and substance in this book when I was a teenager and I stand by it now as one of my favorite books with a
conquer-your-fears-before-they-conquer-you theme. The ending is priceless because Harry actually gives the Whatzit a tip about where to go next because Sheldon Parker's "afraid of everything." Too cute!
As always, if a child's worry, anxiety or fear is extreme and keeps him or her from successfully navigating through normal daily routines, please consult with a certified counselor or a play therapist.