Matthew Gray Gubler, known for his role as Dr. Spencer Reid on "Criminal Minds," surprised fans on his 43rd birthday by announcing his upcoming children's novel, "The Little Kid With the Big Green Hand." He shared the news on Instagram, saying, "I made a new book! It comes out September 26." This is Matthew's first career venture following the premiere of the "Criminal Minds" reboot. Fans showed their excitement and support in the comments, expressing their anticipation for the new book and hoping for another book tour. Matthew previously released his first novel, "Rumple Buttercup: A Story of Bananas, Belonging and Being Yourself," which became a New York Times bestseller in April 2019. The book was so popular that plush versions of the character sold out quickly. This news gives fans some insight into why Matthew has not returned to the "Criminal Minds" franchise. Fans are eagerly awaiting the release of his new book and are excited to see what story it will tell.