It’s not a textbook, if that’s what you mean.
Open it, ctrl+f your search terms.
If it’s not what you’re after, I may have other suggestions but it depends on what you’re after/why Imperialism isn’t helpful.
E.g. are you just after an account of corporate forms? An intro into companies? An explanation of how companies extract wealth from workers? Or how northern companies extract wealth from the global south? A history of the development of companies? A discussion of the role of companies in colonialism? An analysis of the relationship between companies and the state? Info on the role of the state in setting roles on stocks/shares purchases and transfers?
I’d say the bulk of Marxist texts cover private companies in some way. What is it exactly that you want to know?
Not panicking just yet but I’d be sad to see it disappear!