Is this sentence correct?
I've learned that は is a topic marker not an object marker. In this case it's acting as an object marker to 小説 since 読む is transitive a verb.
Now according to the blog I got this from (here) it's supposed to imply that the speaker reads novels but doesn't read other things such as short stories.
One of the functions of は is to imply something applies for the word before the は, but there may be other cases that do not apply.
This implies that the speaker reads novels, but there is probably something he or she doesn’t read (maybe short stories?).