Did Sheikh al-Islam Ibn Taymiyyah author a work stating that Allah's knowledge does not pertain to the infinite and does not encompass the finite, or is this an interpretation of his words, or is it an outright lie and slander?

This slander has no basis in the words or writings of Sheikh al-Islam Ibn Taymiyyah. He, may Allah have mercy on him, ruled that whoever says that Allah Almighty knows only Himself, or knows only universals and not particulars, is a disbeliever, because that is a rejection of the Messenger (peace and blessings of Allah be upon him). Sheikh al-Islam extensively refuted those who deny the attribute of knowledge as subsisting in Allah's essence, explaining that the texts of the Qur'an and Sunnah indicate the affirmation of His detailed knowledge of everything.