According to Chapter 2, were there other books written about Sai Baba before the Sai Satcharitra? If so, which ones are mentioned?

Yes, Chapter 2 of the Sai Satcharitra acknowledges several existing works about Sai Baba. It mentions that Das Ganu had already described the "sweet life of Shri Sai" in three chapters of his book, Bhakta-Lilamrut. Additionally, a knowledge-story told by Sai is found in Chapter 57 of Das Ganu's Santa-Kathamrut. Other sources mentioned in Chapter 2 include Raghunath-Savitri’s Bhajanmala, miscellaneous poems by Das Ganu, Gujarati stories by Amidas and Bhavani Metha, and a series of stories being published in Pune under the name Sai Prabha.