If you are looking for philosophical depth, buy Oppenheim. If you are looking for a practical, result-driven, and student-friendly companion to survive—and even enjoy—Digital Signal Processing, It remains, arguably, the most effective exam-focused DSP textbook ever written for the Indian subcontinent.
His other seminal works, such as "Control Systems" and "Signals and Systems," share the same DNA as his DSP book: rigorous theoretical foundations paired with solved problems. Kani does not write for researchers; he writes for crammers and problem-solvers . He understands the pressure of the Indian engineering semester system—tight deadlines, heavy syllabi, and the need for quick, accurate problem-solving techniques. digital signal processing by nagoor kani