What aspect of MOS opamps are you seeking to learn more about?
A few significant advantages that make MOS based opamps more attractive come to mind. One is the generally lower quiescent power consumption. Another is the higher input impedances associated with MOS technology based opamps. Yet another is the ability of MOS technology based opamps to achieve rail-to-rail output operation. Another advantage that many of the MOS opamps have over bipolar technology based opamps is the ability to operate on lower power supply voltages.
I am sure that there are other advantages as well as a few disadvantages.
Sedra and Smith look at the CMOS op amp in Chapter 9.2 of Microelectronic Circuits. I would also recommend you look at Chapter 6.8 on the Cascode Amplifier as a precursor to Chapter 9.2.