These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Genius Bonus: Aside from the historical and literary references made throughout the book, it's highly unlikely that the target demographic, even in the 60's, would have recognized Damon and Pythias. (Theresa certainly didn't, instead confusing the former with "demon".)
Values Dissonance: Many modern readers, particularly in the current economic climate and with the close-knit family that stays together no longer a prominent value as it was during the Depression or The Fifties, would be puzzled if not annoyed by Robin's central dilemma and especially her difficulty in resolving it—since to them it would seem a no-brainer to choose staying in one place, in a permanent, stable home where you could receive proper schooling, access to fine things, and a chance to have friends and better yourself, even if it meant leaving your family behind.note Many families adopted their children out to rich relatives or friends for exactly that purpose... and then there were the Children's Aid Societies and the orphan trains. Either that, or not knowing what it was like to live during the Depression and thanks to the modern view of the Idle Rich/Fiction500, they'd be appalled she'd even consider abandoning her family just to live in the lap of luxury.
Values Resonance: At the same time, Robin's desires to be independent, make her own choices, and live her own life would resonate with anyone who believes in fairness and equality (particularly for women), and both her love of books and culture and her desire to see a thing of historical significance preserved and restored are timely notions which are still relevant today. The lesson that people are more important than places and objects is also still quite applicable, particularly when modern decadence is contrasted with a time of paucity like the Depression or the current recession.