Wookieepedia: Wiki encyclopedia on the Star Wars universe

Oh man, you have no idea. The 16 year gap between Jedi in 83 and Phantom Menace in 99 was a huge pit of consumer demand for more Star Wars content that was filled by licensed novels. An unimaginable number of pages were written in that time, as a star wars obsessed teen I did my best to read them all. Literally anything you can imagine was tried - evil clone of Luke named Luuke? Check. 10+ novel series about that one x-wing squadron in A New Hope? You best believe it. An alien shown in a move for only for a few seconds? Yep, you get a trilogy too. The quality varied a lot, much of it laughably bad but also many books with stories vastly superior to anything in later movies (the Thrawn trilogy is particularly good.)

George Lucas created a great story with rich visuals from lots of various prior art, that I find interesting to understand (e.g. source: https://www.wired.com/2016/01/valerian-laureline-star-wars/)