I've read both. There is a difference between writing fiction and writing songs. I know, because as a tech writer I can be objective. I write neither; my analysis of Steinbeck and Dylan is based on my enjoyment of reading their work, not comparing it to mine. Both are superb.
I've written both.
In spite of the common misconception that the popular song is purely the product of innate talent and some fortunate inspiration from the ether, it is a craft. It takes hard work to write a decent song, and nobody worked harder than Bob Dylan.
That being said, a brilliant popular song is like a brilliant chapter in a book. A novel is a more substantial undertaking, and while Bob Dylan reached the pinnacle of skill in lyric writing, I suspect the decision to award him the Pulitzer Prize in literature was influenced by sentimentality and the desire by Boomers to enshrine their juvenile rebellion -- of which Dylan is perhaps the most beloved symbol.
As for rap music, we used to compose chants of similar quality and character. When we were ten years old.