First of all, you must pay attention to the fact that one can't relate anything he/she reads in any book to the Shia school of thought as a whole.  Your question which stems from a book by an author not so famous unfortunately hasn’t observed this fact. Anyways, to inform you in short, there have been a group of Sunni scholars and a few Shia scholars who believed in the alteration of the Quran or omission of some of its verses; yet most scholars of both sects have rejected this theory. Therefore, this matter shouldn’t cause conflict between Muslims. If a scholar from either sect says something, it doesn’t mean that the entire sect says the same thing. As for the protection of dhikr which has been spoken of in Surah Hijr[1], some Quranic commentators have said it means the protection of the Quran, while others say that the protection of the prophet (pbuh) is meant[2]. Verses 10 and 11 of Surah Talaq can be considered confirmations for the latter[3]. Regardless of what is meant by the term dhikr, what the verse is saying is that the divine message of the prophet (pbuh) will remain forever and there are no chances of it perishing; that is why today we see that no matter how much the enemies of Islam try, they fail to stop its spread, and it continues to grow by the day amongst the people of the world. Also keep in mind that all of those who believe in the alteration of the Quran, believe that the current Quran that we have in our hands today is enough for our salvation and there are no excuses for it to be disregarded and put to the side. For further information, you can refer to questions:

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