-  Surely those who believe, and those who are Jews, and the Christians, and the Sabians, whoever believes in Allah and the Last day and does good, they shall have their reward from their Lord, and there is no fear for them, nor shall they grieve.
According to this verse if we as the followers of the book follow our books we have nothing to fear.
How can we follow a book that has been lost and does not exist according to present-day Muslims?
In other verses Allah is saying we need to follow additional revelation in addition to the books that we already have.
-  Say: O followers of the Book! you follow no good till you keep up the Taurat and the Injeel and that which is revealed to you from your Lord; and surely that which has been revealed to you from your Lord shall make many of them increase in inordinacy and unbelief; grieve not therefore for the unbelieving people.
This contradicts what he has already said, that followers of the book can follow their books and have nothing to fear:
-  Surely those who believe and those who are Jews and the Sabians and the Christians whoever believes in Allah and the last day and does good– they shall have no fear nor shall they grieve.
No need for additional revelation, i.e. the Koran.
Now Allah commands his prophet to fight the people of the book:
[9.29] Fight those who do not believe in Allah, nor in the latter day, nor do they prohibit what Allah and His Apostle have prohibited, nor follow the religion of truth, out of those who have been given the Book, until they pay the tax in acknowledgment of superiority and they are in a state of subjection.
It is narrated on the authority of Abu Huraira that when the Messenger of Allah (may peace be upon him) breathed his last and Abu Bakr was appointed as his successor (Caliph), those amongst the Arabs who wanted to become apostates became apostates. ‘Umar b. Khattab said to Abu Bakr: Why would you fight against the people, when the Messenger of Allah declared: I have been directed to fight against people so long as they do not say: There is no god but Allah, and he who professed it was granted full protection of his property and life on my behalf except for a right? His (other) affairs rest with Allah. Upon this Abu Bakr said: By Allah, I would definitely fight against him who severed prayer from Zakat, for it is the obligation upon the rich. By Allah, I would fight against them even to secure the cord (used for hobbling the feet of a camel) which they used to give to the Messenger of Allah (as zakat) but now they have withheld it. Umar b. Khattab remarked: By Allah, I found nothing but the fact that Allah had opened the heart of Abu Bakr for (perceiving the justification of) fighting (against those who refused to pay Zakat) and I fully recognized that the (stand of Abu Bakr) was right. (Sahih Muslim, Book 001, Number 0029)
It is reported on the authority of Abu Huraira that the Messenger of Allah said: I have been commanded to fight against people so long as they do not declare that there is no god but Allah, and he who professed it was guaranteed the protection of his property and life on my behalf except for the right affairs rest with Allah. (Sahih Muslim, Book 001, Number 0030)
It is narrated on the authority of Jabir that the Messenger of Allah said: I have been commanded that I should fight against people till they declare that there is no god but Allah, and when they profess it that there is no god but Allah, their blood and riches are guaranteed protection on my behalf except where it is justified by law, and their affairs rest with Allah, and then he (the Holy Prophet) recited (this verse of the Holy Qur’an): “Thou art not over them a warden” (lxxxviii, 22). (Sahih Muslim, Book 001, Number 0032)
It has been narrated on the authority of Abdullah b. ‘Umar that the Messenger of Allah said: I have been commanded to fight against people till they testify that there is no god but Allah, that Muhammad is the messenger of Allah, and they establish prayer, and pay Zakat and if they do it, their blood and property are guaranteed protection on my behalf except when justified by law, and their affairs rest with Allah. (Sahih Muslim, Book 001, Number 0033)
And he (peace and blessings of Allaah be upon him) said: “I have been sent just before the Hour with the sword, so that Allaah will be worshipped ALONE with no partner or associate.” Narrated by Ahmad, 4869; classed as saheeh by al-Albaani in Saheeh al-Jaami’, 2831. (Question No. 34647: The reason why jihaad is prescribed; source; capital and underline emphasis ours)