"Transgress the literary/genre fiction divide"

"The novel transgresses the literary/genre fiction divide."

Is it proper to say that something transgresses a divide? Is a binary also transgressed? and can we use use the slash punctuation for the binary opposites as in here?

Yes, what you wrote is fine. A quick Web search provided some examples:

. . . it is also problematic because it transgresses the public–private law divide inherent to Swedish law. (https://onlinelibrary.wiley.com/doi/10.1111/1468-2427.12651)

. . . a longstanding Mediterranean identity that transgresses the Europe-Africa-divide. (https://www.bigsas-litfestival.com/) (The second hyphen in this example is unusual and unnecessary.)

Those examples use a hyphen, but there is no reason why a slash couldn't also be used to indicate such a division.