It was written to challenge this verse of the Qur'an:
And if you are in doubt about what We have revealed (the Quran) to Our
worshiper (Muhammad), then produce a chapter like it, and call your
witnesses (supporters and helpers) besides God if you are truthful.
http://quran.com/2/23
This verse asks for challenging this Surah but the author misunderstood it and thought it was asking about the whole Qur'an. The book is written based on the authors own interpretation of this verse which obviously isn't correct.
According to US state department, its author, Dr. Shorrosh claimed the book is similar to the Koran "in style and substance ... but contains the gospel message."
But folks at Christianity.SE seems to disagree with his claims. This post about it in Christianity.SE says:
... as a whole, it does not fit in any form of Christianity, not even
the writer's. The idea of the book "The True Furqan", itself, is
ridiculous and do not comply with any doctrinal positions of
Christianity. As you should have understood until here, it is a tool
to be used against Muslims, but destined to fail for obvious reasons.
It challenges the Qur'an but most of it seems to be plagiarized from the Qur'an. The author reworded some verses of the Qur'an and combined it with his beliefs to write this. The following examples show how he did this (Plagiarized and rephrased verses are bolded):
The Quran:
1.Ha, Meem. 2.By the clear Book, 3.Indeed, We have made it an Arabic Qur'an that you might understand. 4.And indeed it is, in the Mother of the Book with Us, exalted and full of wisdom. http://quran.com/43
The True Furqan:
1.O, you who have gone astray from among Our faithful followers: We have inspired it -a True Furqan- in the Arabic tongue clearly miraculous, to distinguish triviality from truth. (4:1)
The Quran:
And when it is said to them, "Believe as the people have believed," they say, "Should we believe as the foolish have believed?" Unquestionably, it is they who are the foolish, but they know [it] not. http://quran.com/2/13
The True Furqan:
Whenever it is urged upon the infidels to believe in The True Furqan, which We revealed, just as Our devoted followers have done, they proclaim, "Are we to accept what the inferior infidels have believed?" (4:7)
The Quran:
In the name of Allah, the Compassionate, the Merciful.
http://quran.com/112
The True Furqan:
1.In the Name of the Father, the Word, the Holy Spirit, the One and only True God. (Chapter A)
P.S. I would like you to watch this video which shows the arabic skills of the author.