Mainly to answer questions like, what is the origin of nationalism, why throughout history it has been more influential than class interest, what is 'the national question'?
I found this reading list online, is it a good place to start? https://fivebooks.com/reader-list/nationalism-nino_gozalishvili/
Not primarily on Nationalism, but in Wretched of the Earth, Frantz Fanon makes a good argument for revolutionary nationalism as a means of uniting the colonized.
I have not read any books on the reading list. I imagine Oxford doesn't have much to say about class interest but I don't know.
These are good bits on the national question (some mentions of nationalism):
I was going to recommend Hobsbawm and Anderson, but you got them covered already.
The invention of tradition is another Hobsbawm (this one collaborative) project that is very elucidating.
I am actually currently reading "From People into Nations" by John Conolly atm and it's an examination of the birth of nationalism in a specific Eastern Europe / Western Slavia context.
Author is a bit of a lib; takes a page to do a mild anticommunism in the introduction and falls prey to some great man thinking when it comes to salon-going poets and linguists but for the most part it's a decent examination of nationalism as an assertive response to being culturally smothered by 18th century European "Germanification" as an example.
Word of warning though it's a fucking tome and probably not a great recommendation as a starter.