Tarkin is definitely the most iffy entry in the new Star Wars canon that I have encountered...oddly enough because it adheres so strongly to the old EU.
Don't get me wrong, I freaked out when I saw that Armand Isard was in the book, because his daughter is one of the most memorable Star Wars villains the EU gave us. But even the inclusion of Interdictors had me questioning things, because the hyperspace jump of the Republic cruiser in the first season of The Clone Wars suggested that it was possible (if not wise) to jump from a planet into hyperspace, and I don't know if Interdictors would work the same way (certainly not fifteen years before the Battle of Yavin!).
Throw in Victory Star Destroyers (yes, I'm happy they're canon, they're cool), Carrack cruisers (again, really happy, they're one of my faves), Secutor-class Star Destroyers (who? TOO MUCH BURDEN OF EU KNOWLEDGE HERE), and other ships, though, and it starts to get a little jumbled.
A New Dawn was brilliant in how it used so many of its own things to establish that this was a new beginning. Female stormtroopers? Heck, yeah. Female Star Destroyer captains? Amazing. A new resource designed to serve as a plot device and a bit of galaxybuilding? Great! Especially because we hadn't seen it before, and JJM thoroughly explained what it is. It was a perfect jumping-in point.
Tarkin, though, has so many references and nods and inclusions and new characters and old characters, though, that it just becomes a mess. It's clinging too hard to the old EU, and it is also being far too aggressive and assertive--I don't know how much behind-the-scenes info James Luceno had, but if Rebels has the Imperials rolling out a brand-new Nebulon-B Frigate to support its ranks, then nerds are going to be all "Ewwwwww, but the Nebulon-B Frigate was in Tarkin, ten years before Rebels, ewwwwww!" and you're going to run into the exact same chaos that necessitated the termination of the EU in the first place.
I mean, it's understandable to have a vast array of ships in the Imperial Navy, but...there's just so much thrown into this book that makes it feel like it belongs in the Legends realm instead of the Canon realm, and that's not good.
The book itself is enjoyable, but...it's nowhere near the quality of A New Dawn, and I fear that it may end up harming the revolution more than it helps.