My advice: Don't read the DS9 Companion before reading this one. Why? Because you'll agree with my review title.
The DS9 Companion weighs in at a hefty 800 pages, while this REVISED TNG Companion is a mere 384 pages, and that includes about 10 hours more source material than the DS9 one (the four movies and 2 episodes). The missing 416 pages comes from a smaller, compressed font used in certain areas (cast lists, episode notes, and movie summaries), but most of it is due to shorter summaries and notes than used in the DS9 one. I noticed many factoids and behind the scenes anecdotes that could have been included but weren't. The biggest disappointment, I think, came from the Nemesis section which didn't answer certain things (i.e., what were their plans for Seven, and who is this Cmdr. Martin Madden listed in the credits).
That having been said, I have been and always shall be a TNG fan, since I practically grew up on it, so this book provided an interesting perspective on the series. My only real problem with it lies in the fact that sometimes it seems that a little more work could have been put into it (i.e., typos in normal words and in proper nouns, a few mixed-up facts).