What is the correct meaning of "and she believed in the words of her Lord and His books" and "and she believed in the words of her Lord and His book"? Does the difference in readings indicate a distortion of the Qur’an or the loss of its original revelation? And how can different readings that completely change the meaning be accepted?

The Qur'anic readings do not contain contradictory differences; rather, they are either in agreement in meaning or vary in diversity and difference, not contradiction. This diversity has several benefits, including: easing the burden and facilitating matters for the Ummah, increasing their rewards, and enhancing eloquence and inimitability. For example, the reading: ﴿وَصَدَّقَتْ بِكَلِمَاتِ رَبِّهَا وَكُتُبِهِ﴾ (And she believed in the words of her Lord and His Books), and the reading: (and His Book); both are correct. Here, "the Book" refers to the generic sense, encompassing every book that Allah revealed, and this meaning does not contradict the plural reading (and His Books). This diversity was a source of confusion for some Companions, so the Prophet, peace and blessings be upon him, clarified that the Qur'an was revealed in seven ahruf (modes/dialects).