For Mutapa, S. I. G. Mudenge's A Political History of Mutapa is a treasure of a book, despite its age (1988). I'm a fan of Innocent Pikirayi's work on various zimbabwe cultures (we can include Rozwi and Torwa Butua in this), including his 2001 book The Zimbabwe Culture, but he's gone quite a bit further since then in journals like Azania where he, Shadreck Chirikure, and some others have utterly reshaped what we know about those sites. Pikirayi's more recent books touch on heritage and thematic subjects (water history in one case), and are good, but not what you're looking for. He wrote earlier on the archaeological situation with Mutapa in 1993 but I'm not sure what the state of the art (so to speak) is in that instance. Chirikure's journal articles are excellent but his books focus on sustained archaeological discussions, mostly metallurgical, that don't translate well to general readership--but if you go down any rabbit holes, remember his name. Yusuf Juwayeyi has a 2020 history of Chewa society (Archaeology and Oral Tradition in Malawi) that should treat Maravi, and I've heard good things about it although I haven't been able to get a copy myself. A paperback is now out, so I have no excuse not to order it.

If you're interested in heritage issues surrounding Great Zimbabwe (Masvingo) past and present, which is interesting because it's been contentious through colonial and postcolonial eras, Joost Fontein's 2006 The Silence of Great Zimbabwe is a good read, though Chirikure's 2020 Great Zimbabwe: Reclaiming a 'Confiscated' Past is the more up to date option and should be an accessible read.

A bit further south, I like Chirikure's co-authored (with Peter Delius) book on Mapungubwe (Mapungubwe reconsidered) a lot for the broader contextualization it does that links its past up with the 500-years project going on in South Africa, but the Limpopo Valley may be too far south for you. Pikirayi has also written about archaeological evidence and organized societies in the Limpopo Valley and southward but I haven't read that book yet and that really is getting outside of your question.

In terms of works that aren't so academic, however, the standalone offerings have long been kind of disappointing. Some of this owes to the distance between academic discussions and popular focus; some bookshops are putting up reprints of R. N. Hall's work from the beginning of the last century like they're 'new,' and some self-published people like Orford still believe that the importance of southeastern Africa lay solely in its being the biblical Ophir or in being some marker of an ancient pan-African essence or unity, points that are intensely colonial in their appropriative understanding. That's before even getting to the very strange people who talk about spiritual forces at the stone matzimbabwe.

So, these are what I'd suggest: when I teach the survey, I generally have students read Pikirayi's 2001 book as a starting point. If you can get a copy, that's a good place to start. If you can borrow Mudenge, that's still a standard work for Mutapa; you won't find a copy for sale at anything like a reasonable price. Juwayeyi and Chirikure are currently in print. For general histories, though, regional approaches haven't been so common. Alois Mlambo's Becoming Zimbabwe may be the best option there, because it will cover the major zimbabwe states (including Mutapa). Maravi, in my opinion, needs attention that it hasn't been getting aside from Juwayeyi's book on Chewa society--but if I get a chance I'll ask my Lusophone colleagues if there's anything in Portuguese.

Update: I have received my copy of Juwayeyi, and I can affirm that the last two chapters deal with Maravi proper, rise/fall. But the whole is about a longer sweep of Chewa society and culture (mostly via material culture, but with plenty of interpretation) so it may be of interest. I've only dipped into it so far, but it's good if a bit more academic than general readers might want.