I have several of them. I bought them for the "expanded info and pictures"/dictionary aspect to them as opposed to any desire to play the game. I bought all of mine in the early-mid nineties when I wanted every aspect of the Star Wars Galaxy to be explored.

I was also trying to make a LucasArts style adventure game off of Heir to the Empire, and I think the HTTE Sourcebook was the first I bought. I still enjoy pulling them off the shelf and flipping through them, and I have enjoyed looking at some of the newest ones at the bookstore, but I haven't bought any in a long time.