I'm not sure Declassified really needs to be reviewed. Either you're already a Vanguard fan, in which case you've already read this book, or you aren't, in which case this isn't the place to start. (That would be Harbinger, the first novel in the series.)
Declassified breaks up the storytelling by offering four novellas, each set at a different time and featuring different key characters from Vanguard's large cast. And while it's the work of the series' longtime braintrust, there's a surprise or two -- Ward and Dilmore fly solo instead of together, and original editor Marco Palmieri contributes one of the novellas. The stories range from before Harbinger to after Precipice, the most recent novel, and they're not just a casual side trip -- very significant events in the lives of the characters and in the Vanguard story arc appear in these pages. And with only two more novels before Vanguard reaches its end (as planned by its writers, not dictated by sales or any other external force) it's very much a core book in the series. Each of the stories has its pleasures; if anything, the narrower focus of the individual stories may make this an easier experience than the novels sometimes are, as they have so many characters and storylines to balance. It's a good approach, one that would have been worth keeping in the mix if Vanguard continued beyond two more books.
If anyone who's followed the series was wondering whether Marco could write -- don't worry, he doesn't let the team down. As an editor he seemed more concerned than some of his peers with his writers' style, not just their plotting, and that same care is evident here. It's just too bad that the scheduled end of the books makes any more Marco contributions to Vanguard very unlikely.
As for the issue of Vanguard coming to an end: it's good news and bad news. I like the idea that we'll be able to look back at Vanguard as a story, and one that didn't overstay its welcome. More series, and I'm not just thinking in Trek terms, could use that kind of thinking. That doesn't mean I'm happy about Vanguard ending, though; it's been one of the most successful runs of books in the Trek line in the last decade, and I'd happily keep on reading more. Hell, maybe they could do the occasional novella collection like this one, revisiting unexplored scenes throughout the Vanguard timeline.
Oh, and Declassified was the first book I read on my new ebook reader, a Kobo Touch. I bought the print version, of course, but Laura decided we needed dedicated ereaders because the iPad is too backlit, too shiny, too heavy for reading in certain situations. We bought them just as I was about to start reading Declassified, which made it an obvious starting point (damn that tiny print -- you're getting value for your money, but my eyes aren't getting any younger). It was a pretty good experience, with one exception. I'm used to looking at paper and turning pages and just tuning out the physical reality of reading a book. I've been doing it more than forty years now. With the ereader, I was more distracted by the mechanics of the process, holding a different kind of artifact and engaging with it in a somewhat different way. I'll get used to it, and I can easily imagine situations in which I'll be very glad to have an ereader. But for Star Trek and some other core collecting areas, I'll still be buying print.