A to Z Mysteries is a popular series of mysteries for children, written by Ron Roy, illustrated by John Steven Gurney, and published by Random House. The series is generally considered among the best "easy readers" for young children. Wikipedia
The Absent Author, The Bald Bandit, The Canary Caper, The Deadly Dungeon, The Empty Envelope, The Falcon's Feathers, The Goose's Gold, The Haunted Hotel, The Invisible Island, The Jaguar's Jewel, The Kidnapped King, The Lucky Lottery, The Missing Mummy, The Ninth Nugget, The Orange Outlaw, The Panda Puzzle, The Quicksand Question, The Runaway Racehorse, The School Skeleton, The Talking T. Rex, The Unwilling Umpire, The Vampire's Vacation, The White Wolf, The X'ed-out X-ray, The Yellow Yacht, The Zombie Zone, White House White-Out, Detective Camp and Mayflower Treasure