Possibly a book, possibly a series – listened to as an audio book on a car trip in the early 2000’s. The book was from Cracker Barrel (which is apparently Ingram Entertainment titles, if that helps). The book followed three protagonists, a girl and two boys. They traveled to other worlds or alternate universes through tunnels. The other worlds usually had some sort of baseball theme. At least one had a society of gnomes who used it as their court procedures. The girl protagonist was a pitcher. The had a map that helped them find the way – depending on how it was folded, it could show a neighborhood, a city or even be a star map. The antagonists had eyes you could see through, all the way to what was on the other side of their heads – photographs of Manhattan Project scientists showed that many of them were bad guys due to this effect.