R' Dovid Tzvi's work in this field needs to be divided into two parts - positive and negative. The first part consists of his polemics against Wellhausen (available in Hebrew translation here).
An English translation with an introduction and annotations was prepared by Carla Sulzbach as a Masters thesis for McGll University. Although I cannot claim any great proficiency in the subject, I will try to give a basic overview of the subject basing myself as much as I can on Sulzbach.
Wellhausen designed the structure of his hypothesis with a very distinctly Pro-Protestant bias in mind. To this end, he attempted to divide the "pure" prophetic spirit (read Protestant) of the earlier books from the the degenerate legalistic (read Jewish) or ritualistic (read Catholic) aspects of the "later" books.
To accomplished this he placed the P(riestly) code (mainly Leviticus ,etc.) as a later post exilic work reflecting the "Oriental" "degeneration" into excessive legalism whereas the Y, E and the prophetic books all represent the earlier pure prophetic spirit of which Jesus (as interpreted of course by his prophet Martin Luther) was heir .
Enter R' Dovid Tzvi Hoffmann. R' Hoffman singlehandedly shattered Wellhausens elegant structure by conclusively demonstrating that Wellhausens dating made no sense whatsoever and that, if anything, the P document which contained all the hated legalistic "distortions" must be shown to be the earliest document.
Complementing R' Dovid Tzvi's writing was the work of his colleague Prof. Jakob Barth  (R' Ezriel Hildesheimer's son -in-law). Prof. Barth's main opponent was the orientalist Friedrich Delitzsch  who in his Babel and Bible attempted to place the Torah as deriving organically from within its Babylonian background. On Prof. Barth's response see my earlier post on the Beis Vaad.
In the next post, I will discuss the positive aspect of R' Hoffman's biblical scholarship.
 The proto-Nazi overtones of this discussion are clear and cannot be understated. Sulzbach makes the point that one can already see hints of the budding Nazi "doctrine" in the writings of the 19th century biblical scholarship. The supposed "Aryan" origins of Jesus is all of a part with this (L. Ginzberg has a letter relating to this subject.)
 Lest anyone wonder why this obviously agenda driven "scholarship" was given any credence at all. One must try to reconstruct the spirit of the 19th century in which Scinece had made such tremendous strides that Scientists wre vewed as demi-gods and their "critical" methods looked on as infallible. See the article on The Amber Witch at Wikipedia (one of my first attempts at writing anything) for a very clever historical hoax that showed exactly how fallible the "scientists" and their "internal criticims" really were.
While on the subject - here are a few more DH hoaxes - 1- Did Bush Exist - A and B. 2- New Directions in Pooh Studies (one needs to be slightly acquainted with the subject to get all the jokes)
 Yet again, I don't claim any expertise in the subject but to briefly summarize subsequent scholarship, Y. Kaufmann made use of R' Dovid Tzvi's work in the creation of his own version of the hypothesis that was much more Judeo friendly. Since then various hypothetical structures have been created, overturned and then rebuilt as if in some type of caricature of the Hegelian triad (I'm just showing off with that last bit haven't the faintest idea what I mean to say.)
At the moment, R. Whybray's fragmentary hypothesis [3a] dominates the scene (interestingly this is basically the same form of the hypothesis proposed by Italian Chief Rabbi Moshe Dovid Cassutto decades ago. For some reason Cassutto's theory wasn't taken seriously in its time on which we can say "הכל תלוי במזל אפילו ספר תורה שבהיכל" ) but as the WP:DH article very elegantly summarizes "The verities enshrined in older introductions [to the subject of the origins of the Pentateuch] have disappeared, and in their place scholars are confronted by competing theories which are discouragingly numerous, exceedingly complex, and often couched in an expository style that is (to quote John van Seter's description of one seminal work) 'not for the faint-hearted.'"
[3a] Therefore the decsison of Encyclopedia Judaica ('o7) to have R. E. Friedman (a hidebound conservative DH proponent) write the Pentateuch entry (which he uses as if it was his own personal forum to debate his opponents - as does S. Wald in the Talmud entry) seems highly un-encyclopedic. (It certainly wouldn't pass on Wikipedia as it's has a definite POV).
 The biographical situation here is even worse then that of R' Hoffman. I can only refer to some cute stories in Leo Jung's autobiography.
 Interestingly, Delitzsch's father's Franz was known to be a great philo-semite (although he drew the line at Geiger's very contemptuous attitude towards Christianity - see S. Heschel "Geiger and the Jewish Jesus"). See note two of this post. Shnayer Leiman published a memoir from Leopold Greenwald with an interesting story about Delitzsch the elder - partially summarized in this comment. See also "Franz Delitzsch (1812-1890) A Palm-Branch from Judah on His Newly-Covered Grave" by David Kaufmann - The Jewish Quarterly Review, Vol. 2, No. 4, (Jul., 1890), pp. 386-399