Having worked thru' the Kreyszig book as an ugrad in EE, back in the late 70s in India, and then reading the various editions of the same book by Prof. Kreyszig, I am appalled at the mindless apathy for the book as shown in the Amazon website by some readers. For a lack of a better word, I believe that most of these readers have a very warped up sense of applied mathematics - that is mathematics as it applies to solution of engineering problems. Kreyszig's book is a goldmine of information, and its latest edition contains a whole slew of carefully chosen problems that are worked out plus homework exercises to aid the student in mastering the necessary analytical techniques essential to solving problems.
I have observed that of late in USA there is a lot of acerbic hostility towards mathematics. Most of the readers (including the teacher and the taught) express their displeasure if they cannot " sell " mathematics like some commodities in a grocery store. The students on the other hand, being too pampered by the existing escapism in a society are reluctant to accept the rigors of any mathematical training and hence are most unhappy if a math. text demands some discipline in terms of focussed concentration and thinking. It is excepected and unfortunate that such critics shall continue to judge such well-written and comprehensive texts on applied mathematics (such as Kreyszig) most boring and their displeasure is a substitute for more cogent and incisive analytical review.