I'll paraphrase what I posted in Reference - good score for $4!
That said, I've always felt the 'Worlds of the Federation' was alright, but that the Spaceflight Chronology, '79 edition, is superior in terms of a believable future history for the Trek universe.
The later editions, in '91 & '96 were obligated to try and cram in all the newer material from the films, TNG and DS9. The 1979 edition also has tons of illustrations and art that are very much better than the screenshots and pictures that were in the later two editions.