Although I am merely a novice programmer (who has taken the offbeaten track to learn the majority of C first), in my opinion some or atleast to an extent, these "300+ page" books are "diluted". I noticed this in 2 programming book and science books in general.
As an example, take the legendary "The C Programming Language" by Kernighan and Ritchie. This is the book im currently on at the moment (the first "proper" textbook). In the preface they mention about the "brevity" they wish to maintain in the book. And they were spot on. One source code accompanied by a paragraph breakdown leaves me thinking, revising and questioning certain aspects for a loooong time. Whereas something like, say, "thinking in C++" has a section on "C background", dare I say that this section was waaaaay less informative, obviously being a C++ book, however, it rambled on to such an extent that the pages it used, one could sqeeze in a good portion of Kernighans C. And it was in no way more informative or revealing. I did say some/to an extent of these 300+ page textbooks.