Shaykh Yasir Qadhi provides an in depth analysis of chapters 38, 39, 40 and 41 of the book - Kitaab At Tawheed.
Chapter 38 tells us that whoever obeys the Scholars and the Rulers, forbidding what Allah has made permissible and permitting what He has made forbidden, has certainly taken them as Lords (besides Allah). The topics that are addressed here are - pointing out the meaning of worship that was initially denied by Adi RA and how conditions have changed to the point that the worship of monks has become the best of deeds under the name of Al-Wilayah (sainthood), while the worship of learned men in religion is considered knowledge and understanding.
Chapter 39 deals with seeking judgement from anyone other than Allah and His Messenger being an act of hypocrisy.the topics discussed are - explanation of the verse in An-Nisa' (4:60), the verse in Al-Baqarah (2:11),the verse in Al-A’raf (7:56), the verse in Al-Ma'idah (5:50), the difference between true lman, and the false and feigned Belief, the incidence of Umar RA with the Munafiq (hypocrite) and how nobody attains lman (Belief) until his all desires are in accordance with what Allah's Messenger ﷺ came with.
Chapter 40 is about those who denies any of the Names and Attributes of Allah. We come across discussions on topics such as - the denial of any of the Names or Attributes of Allah casts out one from Iman, mentioning the reasons which lead to the denial of Allah and His Messenger ﷺ even unintentionally.
Chapter 41 is about recognizing the Grace of Allah, yet denying it which amounts to disbelief. We are made aware of the recognition of the blessings and description of their denial.