I love Victorian literature. I love the big, messy plots; the outlandish characters; and especially the way so many Victorian authors (Charles Dickens in particular) peeled away what they saw as the veneer of superiority held by the upper classes to look at the hypocrisy and corruption underneath class distinctions. In short, everything most people hate about Victorian novels I love.
Be that as it may, I really do think that The Moonstone is one of those books that pretty much anyone will enjoy. Written by Wilkie Collins in 1868, it's considered one of the first English detective novels, and the forefather of the Sherlock Holmes series. The story centers around the theft of a storied (and cursed) diamond, and contains some truly excellent and jaw-dropping plot twists as befits any Victorian novel worth the name.
I think what makes The Moonstone so readable is its concentration on both plot and character. The novel is epistolary--narratives that were written by certain principal characters and sent to the main investigator (Franklin Blake) after the theft. This means readers get several points of view about events relevant to the theft, all of which combine to identify the true culprit. I've heard that Collins began writing The Moonstone after witnessing testimony at a sensational London trial, and the effect is truly like an episode of Law & Order only with anti-colonial messages and opium use instead of quips from Detective Briscoe.
Best of all? The Moonstone is in the public domain, so if you have an e-reader you can almost certainly find it as a free download. Hooray for free books!