The Prince and the Pauper
The Prince and the Pauper by Mark Twain.
A pauper can prince, but can a prince pauper?
Like the Tom Sawyer books I struggled reading the archaic English to begin with, but I'm glad I stuck with it. These days the overall plot would be considered a pretty standard 'Freaky Friday' type deal; two very different people learn to appreciate their own circumstances by switching places, but even after 150-odd years of similar stories Twain's still stands out.
Both the pauper-turned-prince and prince-turned-pauper acquit themselves admirably over the course of the book despite obvious difficulties in adapting to their new circumstance; thanks in no small part to one Miles Hendon. The prince never quite stops acting like a spoiled brat, but he adapts well enough for someone raised from birth to think themselves a god. Meanwhile the pauper makes an almost unbelievably effective ruler despite predictably being corrupted to some extent by his sudden power and riches.
In the end it's all wrapped up in a believable and satisfying way, no glaring potholes to be found despite a genuinely unbelievable scenario. Definitely worth a read if you enjoy Twain's general 'boys bullshit their way through crazy situations' vibe.