I really like her - she and McKee are my number one and two non-Dramatica storytelling manuals. I agree, she's fantastic on theme and its relationship to character and plot.
Her Transformational Arc is another 10 or 15 or 22 steps approach to standardizing a story approach to psychological growth, but it's a really good one, and really nicely explains how the A, B, and C stories tie together to tell a united story - A being Dramatica's OS, B "subplot" is the MC, and C "subplot" is the IC and RS collapsed into one. So when I hit a Dramatica wall, I'll pick up Marks and take what I guess is the more subjective storytelling approach for a while.
And yes, agreed with @jhull the examples are really dated but the payoff is her use of those examples to give explanations and demonstrations of how to make it all work are very strong.
Yes also, she doesn't acknowledge steadfast characters except in tragedy, where tragic heroes - her example is Henry Hill in Goodfellas - fails to learn and therefore takes a tragic arc towards a Dramatica Failure/Bad ending. Also in old Hollywood story guru style she insists a Protagonist (who she defines as must carry the goal of the plot) must also be the emotional heart of the story, so her view only allows for what Dramatica calls "Heroes". Still, with adjustments for a Dramatica view that you need for using any other story theorist, I think it's a really useful book. Hope you find her helpful.