Asalam Alykum WrWb I have heard the audio lectures of Shaykh Hamza Yusuf in which he used Martin Lings book. Its a good book to read for seerah literature but as mentioned by Shaykh, Martin lings does go a bit astray in few parts of the book. So best is to listen to the audio, Shaykh Hamza Yusuf rectifys the mistakes Martin Lings has made.