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"!
This thread has been interesting for me. The first time I've opened the book in 13-14 years probably. Not exactly what I remembered. So just ignore my posts :)
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"!