http://www.newmanreader.org/works/idea/

Men whose life lies in the cultivation of one science, or the exercise of one method of thought, have no more right, though they have often more ambition, to generalize .upon the basis of their own pursuit but beyond its range, than the schoolboy or the ploughman to fudge of a Prime Minister.
[…]
He has the obstinacy of the bigot, whom he scorns, without the bigot’s apology, that he has been taught, as he thinks, his doctrine from heaven. Thus he becomes what is commonly called a man of one idea; which properly means a man of one science, and of the view, partly true, but subordinate, partly false, which is all that can proceed out of anything so partial. hence it is that we have the principles of utility, of combination, of progress, of philanthropy, or, in material sciences, comparative anatomy, phrenology, electricity, exalted into leading ideas, and keys, if not of all knowledge, at least of many things more than belong to them-principles, all of them true to a certain point, yet all degenerating into error and quackery, because they are carried to excess, viz., at the point l where they require interpretation and restraint from other quarters, and because they are employed to do what is simply too much for them, inasmuch as a little science is not deep philosophy.
[…]
But of these conceits Aristotle speaketh seriously and wisely when he saith, “Qui respiciunt ad pauca, de facili pronunciant [They who contemplate a few things have no difficulty in deciding].’ ” [The Idea of a University, 108-109]

I have not read all of the Summa Theologica, but yet, I would not hesitate to put it on this list. The same could be said of other books.

Newman is comparable to John Owen or Aquinas. He is very thorough about his argumentation, so that it turns out to be very compelling. In fact, his whole book (400 pages) is dedicated to answering only two questions:

Whether it is consistent with the idea of university teaching to exclude theology from a place among the sciences which it embraces [this takes about ¼ of the book].

Whether it is consistent with that idea to make the useful arts and sciences its direct and principal concern, to the neglect of those liberal studies and exercises of mind in which it has heretofore been considered mainly to consist [Discourse II, introductory paragraph].

So, while it is necessary to read some books in their entirety before coming to the conclusion that they are good books, it is only necessary to read a few chapters of others to conclude that they are great works.

I like to side with Father Brown in saying that it would be inconsistent with the character of Newman to have a great first part of the book and a bad last part.