A respectable update to a classic hard sci-fi setting. What it lacks in nitty-gritty details in some areas it makes up for breadth of coverage.
THE BAD NEWS FIRST
If you're looking for a lavishly-illustrated book like the original, you're going to be very disappointed with this. Art is sparse in here, although generally pretty decent. This book favors density of information over artistic beauty, and it covers a LOT of ground in its 314 pages.
There's a couple of editing & formatting errors. A half-page is blank where I'm guessing they intended to put a picture but changed their minds at the last minute. Some of the tables are a little hard to read at first. A couple of the nation profiles in the core worlds have the wrong population digit, and Tirane is lacking its UWP. These last issues are pretty easy to get the right numbers when you read the description. Tirane, for instance, is pretty much Earth's twin with interface A, and probably one digit lower for population & law level.
I'd describe 2300ad as a mildly dystopian, hard-sci-fi setting in the tradition of movies like Alien, Outland, or Gattaca. In Traveller terms, it's roughly Tech Level 12, with some areas like genetic engineering as high as Tech Level 16. However, there are a number of Traveller-standbys that don't exist: reactionless maneuver drives, jump drive, gravity control and antigravity vehicles, and meson guns & communicators.
Many current nations still exist, albeit in different forms or with different roles. Peculiarities of the stuttewarp drive (which acts like an STL or an FTL drive depending on how deep in a star's gravity well the craft is) have limited exploration along three "arms" of local space, named for the dominant power in each: American, Chinese, & French. France is the aging superpower if 2300ad, with China (specifically Manchuria) a close second and a resurgent America trailing behind. About 30 worlds have colonies, and there almost as many outposts. Some potential new colony worlds are also detailed.
There are 5 alien species, ranging from the nearly human (but almost religously technocratic) Sung to the Petapods (who treat DNA like tinkertoys). Only the most recently encountered species, the insect-like Kaefers ("Bugs" in German), has proven a genuine threat to human dominance of the 50 or so light-year spehere of human exploration.
2300ad uses rules from the Core Rulebook, High-Guard, Central Supply Catalog, & the new Vehicle Handbook. However, all the relevant non-Core rules are repeated here for your convenience.
Character creation has some significant differences: the card-deck based character motivations are ported from the original GDW game, and there's a whole system of character traits similar to the alien species traits in the core rulebook.
Characters have to pick a nationality, and if they're from one of the frontier worlds they will also have a DNA modification. The character traits may grant bonuses or penalties (sometimes both), and add an additional layer of depth to characters.
There's also more detailed rules for operating in different gravities from your home world: these are modifications to characteristics. There's also rules to acclimating to different planetary environments (Planetary Adaptation Syndrome).
Not only does the book include NPC stats, but there's a system for generating quick NPC's for any occasion.
Starship construction & combat are re-vamped. Construction is generally similar, with more options available than traditional Mongoose-Traveller ships.
Space combat in 2300ad is very different than standard Traveller: I would compare it more to submarine warfare than age-of-sail gun battles. The dominant weapons are missiles: which in 2300ad work more like kamikaze drones than fire & forget weapons. Finding the general location of an enemy ship is easy (there is no stealth in space), but getting a firing solution on a rapidly-moving stutterwarp ship can be tricky. If your ship doesn't have a good enough sensors package, you may literally end up just shooting in the dark.
COMPARISONS TO THE ORIGINAL
The setting's background has been tweaked: the "bad things" are moved up from the late 1990's to the mid-21st century. Dates & details are left deliberately vague, explained by a combination of loss of records, social taboos, and government suppression.
Technology has been re-worked slightly, there's some mild transhumanist elements, and there's explanations of why AI hasn't become more commonplace. Computers & related technologies have been updated to be more plausible.
Overall the equipment selection is very good: there's a wide range of gear available for exploration or military-style adventuring. While fans of "gun porn" might be disappointed with the lack of illustrations, there's ample description: the new version has 48 varieties of personally-carried mayhem, to the original's 37. Most, if not all of the favorites from the original Adventurer's guide show up, plus several others only seen in supplements.
Fewer starships are listed, although there's at least one of each type in the book: a fighter, an exploratory ship, a frigate, a cruiser, a courier, and a bulk freighter as well as a variety of interface craft. Unlike the previous version, there's an official deck plan for every one.
"Libertine Traders" are a change from the "all starships are owned by transnationals, big foundations, or governments" paradigm of the original. The Libertines remind me vaguely of the merchanters of CJ Cherry's Alliance-Union novels: fiercely independent, and often times somewhat shady.
Much has been made about the lack of Kaefer stats & gear. I actually see this as a feature & not a bug (!). In many respects, the original setting was marred by the dominance of the Kaefer War: GDW seemed to be in a bit of a rut, and much of 2300ad turned into Twilight: 2000 in space with NATO fighting the bugs instead of communists.
In the new version, you can't go bug-hunting right away. You CAN do just about anything else, however: you can run a Firefly-esque game with a Libertine family or a group of troubleshooters in a courier, play (or chase) pirates in a frigate, run cyberpunk or Minority Report adventures in the core, or contend with the harsh realities of colony life on the Frontier. Or you can try exploring some of the potential new colony worlds listed in the book.
[4 of 5 Stars!]