Hmm... Having not seen the first edition of the book (which is the edition you must have given that you used it 15 years ago and it was updated 8 years ago), it

Hmm... Having not seen the first edition of the book (which is the edition you must have given that you used it 15 years ago and it was updated 8 years ago), it's possible that your assessment of its elementary content is specific to that edition. However, the second edition of the text is by no means elementary; unless you are conflating beginner literature with comprehensive literature, and the text is certainly comprehensive. I'll grant you that Chapter 1 is a summary and introduction to the entire book with little challenging or novel material for someone experienced with UNIX and C, but many advanced texts have introductory sections. A large portion of the "The Art of Computer Programming: Fundamental Algorithms" is essentially a review of the elementary mathematics necessary for the analysis of algorithms, but I would never call TAOP a "beginners book"!