Is there any difference between the following two variants: "the novels of Dickens" and "the novels by Dickens". Are both of them equally correct?
Both are "correct." There is some semantic difference, though.
"Novels by Dickens" merely refers to those authored by him.
OTOH, "Novels of Dickens" is a more loaded expression which implies the characteristics of Dickens' writing. Compare also with "Dickens' novels" which is quite the same thing, yet not very explicit in drawing attention to the nature and characteristics as such.
At least that's how one would read the different expressions in general, I'd surmise.
[Google -- Books]
"novels by Dickens": About 5,990 results
"novels of Dickens": About 35,200 results
"Dickens' novels": About 53,000 results
Both are equally correct. The word "of" here means belonging to, and the word "by" means written by, where the written is kind of implicit here. Although slightly different here, both are grammatically correct, and have the same meaning.