I consider the Thrawn trilogy really good fanfiction. Now, I’ve gotta emphasis “really good” over “fanfiction”. I think Zahn fell short with his description of how ysalamari powers work, not to mention inclusion of the Luuke clone and the improbable survival of Anakin’s lightsaber, but the pros far outnumber the cons in my book.
I’ll forever consider Zahn’s Clone Wars the real Clone Wars over Lucas’.