I can't provide the original English novel of the Japanese drama A bouquet for Algernon. This was because the play was adapted from the novel "Flower Dance for Aarón" written by Hiroshima in Japan. The copyright of the English version of the novel belonged to the British publishing company Pim Heartbeat, which had not yet been released to the public. However, you can try to search for the English version of the adaptation, such as "Aaron's Notebook". These works may contain the English version of the play. If you want more information, you can consult the relevant publishing company or translation company.