Jumping into the old Expanded Universe stuff can be a real trip. The Mara Jade novels, especially the ones by Timothy Zahn like 'Heir to the Empire', are basically the foundation of a whole era of fandom that got overwritten. For a new fan, it depends on what you're after. If you're just happy with the movies and Disney+ shows, you might find the whole thing a bit dated and now irrelevant to the main story. But if you're curious about the legendary stuff older fans rant about—where Luke actually rebuilt the Jedi Order and had a complex relationship—Mara is central to that. She starts as the Emperor's Hand, this assassin hunting Luke, and her evolution is a wild ride. The prose can feel very 90s paperback, not as slick as modern stuff, and the tech descriptions are hilariously of their time.
I'd say they're worth it as a historical artifact, a 'what if' timeline that shaped Star Wars for decades. They’re not necessary, but they offer a complete, finished saga for Luke, Han, and Leia that the new canon hasn't provided yet. You get political maneuvering, new villains like Thrawn, and a love story that didn't feel forced. Just brace for a different pace and some lore that clashes with what's official now. I found myself just enjoying it as its own separate thing, like a great fanfiction universe that once was canon.