Title By Author - Commas necessary or optional?

Alice's Adventures in Wonderland by Lewis Carroll is a text that...
Alice's Adventures in Wonderland, by Lewis Caroll, is a text that...

I initially wrote the beginning of that sentence without the commas like in the first example I provided, but I was corrected by a professor. I have never been corrected in this way before so I am curious as to whether this is a style preference or the first sentence is definitively wrong and other professors have missed it.