The book is great, and it deserves five stars for its quality (hardback, dustcover, inside paper and prints quality). I bought a 2nd hand one for 0,01£ and it really looks like new!
Why "only" 4 stars, then? Because it was published in 1998, and some of the Star Wars universe characters have evolved since then, and you'll miss this information...
Example (SPOILER!): if you read the information about Mara Jade, it is quite good, but it only covers until the time she was romantically involved with L.C., while we know for the SW novels that she ended being Mrs. Skywalker!
Anyway, if you don't mind that the encyclopaedia is not updated, I'd recommend it.