Why are you citing a 20th or 21st century book cover design?

If this font was derived from Roman works, it was primarily derived from sculpture.
Note also it is caps and small caps—no lower case letters.

When fonts like this [for example Trajan] they are considered headline fonts only as they are too hard to read in text.

Study the Trajan font and read how it was designed and see if it is the one on the book cover. There are other similar, like Castellan.

Check out Jupiter
I think it is your font as it has the sweeping downstroke of the “R” and occasional use of oversized “I” and several ligatures [combined letterforms like the “TH” in your sample]

A good word for the style is “chiseled” as it resembles the writings on buildings and statues like the Column of Trajan.

Is the term you’re looking for justified?

It’s not that they don’t use spaces, they just don’t cut words off before the end of the line, and then adjust each line’s spacing so it fills the full width. There is never whitespace to begin or end lines.

just for clarification, the typeface used is Mantinia… it’s listed in the link @ParaParaYukiko provided

I thought that Roman Latin didn’t use lower case – it was a medieval innovation.

The link to the description of the font provided by @funkdaddy provides some key points ot include. It mentions the font contains several ligatures that are more common in stone engraving than in type, and that the font is inscriptional. The use of ligatures rather than kerning to adjust the font is interesting.

Here’s an interview with the author of Space Between Words: The Origins of Silent Reading than you might find interesting.

@funkdaddy Yes, I guess justified would be the best term to describe what I’m talking about. Thank you!

@anartist I’m citing the book cover as an example of contemporary typography emulating very early usage of letterforms, reflecting the content of the writing. The book was originally written by a Roman emperor who lived during the 2nd century AD.
And even though Jupiter isn’t the typeface used… it’s still a very lovely font!

@BarnacleBill Thank you for the link to that interview! That’s something I hadn’t thought about.