Indeed this book, Zaad al Ma’aad fee Hadyi Khayr al ‘Ibaad by al Imaam Ibnul Qayyim is an excellent book that is exceptional in its topic area.
The topic of the book is the life of the Messenger – صلى الله عليه وسلم – and all that the word ‘life’ consists of. So it deals with the Seerah of the Prophet, but the author would include matters of Fiqh, mannerisms, advice and other information.
He would speak about the Messenger’s – صلى الله عليه وسلم – Seerah, his worship, his day to day life and his interactions with his companions as well as his enemies.
He would verify the authenticity of Ahadeeth cited, declaring some to be authentic and others not.
He would derive points of benefit from authentic or preponderant Ahadeeth.
He would derive issues related to Fiqh from the authentic or preponderant Ahadeeth and discard the weaker narrations.
He would gather the opinions of the scholars on an issue and follow the evidence in his choices.
He would elaborate on intricate issues and deep points that one could not be guided to except a person whom Allah has blessed with great knowledge and understanding – which is something that is to be expected from the author.