One (though hardly the only) remarkable thing about the
K&R book is indeed its thinness; it is a
great book not despite, but rather (in part)
because of its
brevity. It is the epitome of
pithiness, and not at all in any negative sense, either -- the book packs a huge amount of information, but it presents its truths
simply, without decoration or repetition or mind-numbing chapter-end summaries. It is a book to be read
carefully, and several times, because if you miss or aren't ready for any of its many pieces of
keen advice when you pass over them, you don't get a second chance.
The thinness of K&R is of course in marked contrast to just about every other "modern" programming book on the market. (The briefest of glances at the software section of a technical bookstore reveals thicker and thicker books on narrower and narrower topics.)
Rather amusingly, a year or two ago Prentice-Hall started printing K&R on thicker paper, so that (although it contains the exact same number of pages) it now doesn't get quite so lost on the shelves next to all the bloatware books...