What is the opinion on the book "Al-Ibānah 'an Sharī'at al-Firqah al-Nājiyah wa Mujānabat al-Firaq al-Madhmūmah" by Ibn Baṭṭah al-'Ukbari?

This book is one of the important references for understanding the creed of the Salaf, and its author is one of their early scholars. It has been authenticated by Dr. Reda Na'san Mo'ti.