the Online material by ISC cc is best
second resource you can use in Mike Chappel's cc book
please use chat gpt as well- when there are many terms ask chat gpt to print in table format e.g OSI model and the data type used at each layers, and network devices used at each layer, ask chat gpt to print questions on each topic- this really helps to understand the difference
Save all in table format and revise all again in end.
