I wholeheartedly recommend the Landmark Herodotus: https://www.amazon.ca/Landmark-Herodotus-Histories-Robert-St...

The indices, maps, and other additional information was a great aid in understanding the text.

I agree, and I don't think I appreciated this point enough when I was in school. In high school or college, I would do literally what is said here - get assigned a book, and read the book. In my professional reading, or also hobby reading as an adult, I would never approach learning a topic that way. As an adult, I supplement my reading of a text with secondary sources about the text (things people have written about the text, wikipedia articles about the text or things in it, etc.).

To take an example of an edition that does this really well: the "Landmark" series for Thucydides [1] and Herodotus [2] both qualify as "big, difficult" books, but the book comes with additional secondary sources that aid in the reading to orient the newbie in how to approach the text.

[1] https://www.amazon.com/Landmark-Thucydides-Comprehensive-Gui... [2] https://www.amazon.com/Landmark-Herodotus-Histories-Robert-S...