What is Michael morpurgos saddest book?

One of Michael Morpurgo's saddest books is "War Horse," which tells the poignant story of a horse named Joey who serves in World War I. The narrative explores themes of loss, separation, and the brutality of war, as Joey navigates the horrors of battle while longing for his beloved owner, Albert. The emotional depth of the characters and their experiences evokes a profound sense of sorrow, making it a heart-wrenching read.