You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Gamal_Abdel_Nasser

Context:
The Egyptian singer Umm Kulthum hosted a public celebration for the officers' return despite reservations from the royal government, which had been pressured by the British to prevent the reception. The apparent difference in attitude between the government and the general public increased Nasser's determination to topple the monarchy. Nasser had also felt bitter that his brigade had not been relieved despite the resilience it displayed. He started writing his book Philosophy of the Revolution during the siege.

Question:
What book did Nasser start writing?

Philosophy of the Revolution