In August 1791 began the uprising that paved the way for the abolition of the transatlantic slave trade. Unesco commemorates this mutiny with the International Day for the Remembrance of the Slave Trade and its Abolition with the aim of "inscrib[ing] the tragedy of the slave trade in the memory of all peoples". But retelling traumatic events can prove to be challenging, more so if the audience is young. One of the easiest ways of imparting difficult lessons is perhaps through stories. Yet, as two recent picture books about slavery show, this is no easy task either. Both A Fine Dessert and A Birthday Cake for George Washington have a similar premise - American slaves in the kitchen - and the objections against both are much the same too - the depiction of the slaves as happy and, more importantly, as smiling.

There is nothing good about slavery, detractors argue; how then can a slave be happy? But those living in bondage certainly did celebrate the courage to live through slavery - it is what kept them going. The problem, thus, is not the smiling slave girl; it is the lack of context. A Birthday Cake for George Washington portrays a real character, Hercules, an enslaved African owned by George Washington and forced to work as his chef, and his daughter gleefully baking a birthday cake for the president. But a key fact that the author acknowledges in a note but omits from the book's cheerful primary text and illustrations is that after he was punished with menial labour, Hercules escaped from Washington's household, leaving his daughter behind. Since slavery continues to have a lasting impact on the American landscape, it is important not to leave out the uncomfortable parts.

The trick is to telegraph injustice in a phrase or a glance, without unduly frightening the readers or unwisely letting them off the hook. In Words Set Me Free: The Story of Young Frederick Douglass, a striking diptych shows the 8-year-old hero gazing at the blue sky from the deck of a boat (picture). Frederick is leaving the plantation where he was treated like an animal, the text and the wistful expression on his face indicate his wonder at the world outside. Then the eyes fall to the bottom of the page and one sees that Frederick is still a captive: his hands are secured with thick yellow rope.

Writers and publishers should also ask themselves how they want to present the truth and what they want children to take away at the end of the book. In Love Twelve Miles Long, a mother walks 12 miles to meet her son. When the child asks her how she can walk so far, she recounts her journey mile by mile. Every difficulty she faces on the way bears testament to the unbreakable spirit of the black slaves, and every hardship is worth it as it brings mother and son closer. Dark, foreboding scenes of the journey are balanced with touching images of a smiling mother and son conversing in soft candlelight. The real-life horrors lurk just behind the text, ever-present but never explicit enough to scare off readers from engaging with the subject.