I'd prefer one that focuses more on how it was structured and functioned rather than on a broad history of events.

You have to narrow down what you're asking about. "The Spanish Empire" is a vast subject, and if you want the nuts and bolts of it-- you have to specify just which nuts and which bolts you're interested in. "All of it" -- that's an entire academic career.

So are you interested in how the Viceroyalty of New Spain was run?

Or how Charles V raised money to pay for his wars?

Or the operation of the Cortes in approving the Millones, a tax on food?

Or Philip II's negotiations with Italian bankers?

There are scholars who've deeply researched all these topics and many more-- but you've got to be more specific to get anything more than a survey of spanish history.

Two well known anglophone historians of the Spanish Empire are J.H Elliott and Henry Kamen - they've each written many excellent books touching on the subject, but you'll get much more useful suggestions if you can say just what period you're interested in.