I agree with u/DownvotingCorvo's warning. Since you ask about music, I could make some suggestions. But I want to comment on another warning first.

You ask for books about specific Classical composers. Music history still has a strong great man vibe, it has been that way since the birth of musicology in the 19th century. I think there's nothing wrong about wanting to know about the lives of famous men from the past, I just think WAY too much emphasis is put on those, and a lot of oversimplifications are made when history is told that way.

The big books on the lives of the "Great Composers" could not be considered light reading for most people, and many "accessible" ones I've seen make these oversimplifications I just mentioned, or become some kind of light novel (with blanks filled with cozy feelings and dramatic intentions).

Now, I would recommend the following super accessible books about classical music (they are not about the lives of the famous composers):

• Nicholas Cook's Music: A Very Short Introduction. From its foreword:

So this book is as much about thinking about music as it is about music. And it is also about the social and institutional structures that condition thinking about music. The book begins with an individual, domestic response to music – with a television commercial, and the different associations and connotations that give it meaning – and ends with a snapshot of how people are thinking, and writing, about music in today’s academic world.

• D. Kern Holoman's The Orchestra: A Very Short Introduction. The title is very appropriate. This book tells you about the history of the orchestra, not just about how it started but about what it has gone through more recently.

• Thomas Forrest Kelly's Early Music: A Very Short Introduction. Most of the classical music people come in contact is quite old, but this book is about how we have addressed the matter of classical music that is even a little older.

No, I do not work for Oxford University Press... But I think these casual short introductions are nice little books to get people into important considerations when it comes to the history of classical music, beyond the Beethoven personality cult. For the record, I DO think Beethoven rules, and will probably keep linking to that recording whenever I mention it. Make sure to turn up the volume :)

• Bonus recommendation of the day. Christopher Small's Musicking: The Meanings of Performing and Listening. If you are in the mood for classical music, bits of history, and some reflections on the crazy nature of the rituals in classical music, this book is for you. It's not dense, it's super readable, but it will make you think a lot about this crazy "music from the past" thing.

A lot of (although not all) "accessible" history books have a problem with overgeneralization and bias towards one side, which you should be aware of while reading them. Still, I completely understand how you could be bored by certain academic books that focus on a lot of details and use plenty of jargon. With that in mind, I'd be happy to suggest some books to you for the Aztecs and Mayas subject (sorry I can't for the others, I simply don't know enough about them) that from my experience would fit your criteria of being accessible while also avoiding the issues a lot of popular history books have.

Aztecs

Aztec Warfare: Imperial Expansion and Political Control by Ross Hassig - This one is my favorite book the Aztecs. It's well written, very accurate and thorough, and serves as an excellent jumping off point for learning more about the Aztecs. Mainly discusses the internal workings of the Aztec Empire during wartime, and of course the history of Aztec expansion, and finally the conquest.

Aztec Thought and Culture by Miguel Leon-Portilla - Excellent overview of Aztec culture and will begin to reveal the world of pre-columbian Nahua philosophy to you.

Tlacaelel Remembered: Mastermind of the Aztec Empire by Susan Schroeder - This book just came out, but I've really been enjoying it so far. Might be more academic than you want since it does a lot of discussion about the sources, but if you're already interested in the Aztecs this is a great biography of one of the most important people in their history.

Mayas

Forest of Kings: The Untold Story of the Ancient Maya by David Freidel and Linda Schele - Haven't actually read this one myself but I've been told it's a very good book on what classic maya civilization was like. It's recommended on the Askhistorians book list, which you can find here (https://www.reddit.com/r/AskHistorians/wiki/books), so you know it's good.

The Maya by Michael D. Coe and Stephen Houston - Might contain too many details for you, but it's probably the best general overview of Maya civilization from beginning to end, as opposed to the previous book, which focuses primarily on the classic and epiclassic period.

For the rest of the subjects, check out the booklist I linked, I'm sure you'll be able to find stuff on it there.