If you have found a PDF version, use it ethically and responsibly. Better yet, buy a physical copy. The act of flipping to page 124, annotating the Bode plot, and keeping the book on your desk will serve you longer than any digital download.
The LM324 is presented as a breakthrough in circuit integration, allowing for four independent operational amplifiers to operate from a single power supply. Gayakwad uses this specific IC to transition from theoretical single op-amp circuits to complex, real-world system designs. If you have found a PDF version, use