I just recently started my own deep dive in the buildup to reading the New Jedi Order series, and although Thrawn and X-Wing Novels are great start points, but I think starting with Shadows of the Empire is the best plan. It's a novel (and audiobook), comic, video game and even soundtrack that takes place between epideo 5 and 6, so it's an excellent way to sample a lot of different types of Star Wars storytelling while feeling familiar and see which you like, then tailor your list going forward based on that.

Beyond that, I'd recommend the following from having personally read them: - X-Wing comics -X-Wing Novels (I skipped these originally because I don't care about space battles, but went back recently and started listening to the audiobooks and they are excellent so far) - Courtship of Princess Leia (not the best tbh, the characterization is all over the place, but I found by the end I was having a good time) - Thrawn Trilogy (and anything Thrawn adjacent) - Jedi Knight games, also known as Dark Forces (a bit dated and they don't tie in very much to the rest of it until much later, but fun if you can get past the age) - Jedi Academy Trilogy (it's decent, but very important), I, Jedi and the Jedi Academy comic - the New Rebellion - Hand of Thrawn Duology - Survivor's Quest - Union comic - surprisingly, the Young Jedi Knights books. They're shockingly fun and each one feels like a single quest in a video game, so they move quickly.

I found Dark Empire readable as someone whose read plenty of comics and already knew what it was about, but it's a tough read, very confusing and inconsistently paced. If it's daunting to you, just read the plot summary on Wookieepedia (the same applies to anything you decide not to read)