« Al-Istiqâmah » of Shaykh al-Islam Ibn Taymiyyah - here in its best edition - is a book in which many subjects are covered. Among these topics:
The obligation of steadfastness, of following the Qur'an and the Sunnah,
The Qur'an and Sunnah contain the whole guidance,
The misguidance is the cause of the abandonment of the Qur'an and the Sunnah,
Refutation of the words of the people of kalaam saying the Qur'an and the Sunnah do not contain the basics of religion but that these bases are known by reason,
And many other subjects.