I haven't read Gary' book. But I think razavi's one is very good because it helps designers to expect the circuit behaviour without so much analysis.
But I have a question, If I read razavi's book, am i in need to read Gray's book? will it add new info to me or it's just a different method of explanasion?
four basic books ; razavi , gray & meyer , ken martin ,sansen
1- start by razavi ; simple , intuitive , basics
2- then go through ken martin ; simple , systematic design & practical circuits
3- then get the main points from gray ; rigorous analysis ; important to see the neglected effects by the above 2 books and see when you can consider those effects more deeply
4- for advanced & state of the art ; Sansen book , mainly lectures with added notes
i read them both, with the sequence of razavi first, gray second
i think gray should be first, razavi is more a practical book, if you dont get the basics, you will not see the whole pic,
start with gray