I think it's nice to have for its coverage of all the prime-Enterprise's but could have been so much more. My biggest disappointment was that the book is packed with not especially interesting screenshots and doesn't have nearly as many diagrams as I’d like, which could have given us so much new detail. For instance there's a page on the NX-01's sickbay which is nearly filled with three screencaps, if that was one smaller photo and a nice big diagram showing the layout and details of sickbay that would have been fascinating.
The new diagrams there are, are very nice, though the layout of the book has the unfortunate effect of losing chunks of them in the bit between pages.
Some of the obvious missing stuff is also a bit disappointing; we get features on the NX-01 shuttlepods, standard TOS shuttle, Enterprise-D shuttles of various classes and the Enterprise-E captain's yacht, but don't see the Enterprise-A's shuttles, the rarely seen (and ripe for expansion) Enterprise-E shuttles, the Enterprise-D captain's yacht, or the various TAS shuttles.
I'd also have appreciated a bit more space given to exploring the various changes seen in the 1701 and 1701-A, and particularly missed even having a single image of the pointy nacelled Pike-era Enterprise.
I quite liked the format of the sections dealing with technologies common to all the Enterprise's, I thought that was a good way to deal with them. Though was again left with a feeling of incompleteness with how they did the alternate realities section; it covers the mirror universe, the new universe (with a standard screencap of the new Enterprise) and the multiverse of Enterprises as seen in Parallels, but no hint at the Enterprise-J, the All Good Things.. Enterprise, or the E2 Enterprise. That could have been a fascinating chapter all by itself, but was cramped into four pages.
Anywho, all together it's fun and interesting, but a bit light; it could have been so much more. If you own the Star Trek Fact Files it probably won’t add much, if you only have the previous technical manuals it might be worth picking it up for the bits on the other Enterprises that haven't been featured in a book before.