I'll give you my take on it so far.
The material in the book is pretty good. The functional elements for running a B5 game in Traveller are there. The jump gates and jump point generators, basic weapons, big characters, races, and backstory. It assumes your game is set some time after Sheridan takes over, but info for running a game later is there, too. I'm starting my game between the pilot and first season, so I have to make some deltas for my setting.
The psionics are fleshed out from the Trav main book and given a B5 feel based on specific show events. I have some differences with how some of it is done based on my take from the show, though. Nothing huge, but I'm going to make changes.
The amount of verbage spent on backstory is, to me, excessive. Instead of the space being spent on overly detailed backstory (e.g. the step by step development of PsiCorps predecessor agency) I would have liked to see more basic functional information on B5, a basic map of B5's layout and a couple of "unrolled" maps laying out the general plans for blue, green, and red sector. Or at least a detailed section of each. Anyway, more basic campaign starter stuff by contrast. I'm familiar with B5 but don't have any of the prior RPGs. I'm having to put together a lot of basic play info from The Lurker's Guide that I expected to find in this book.
The ships are a sort of odd neither fish nor fowl mix between Traveller and not-Traveller. Even without jump drives as in Traveller, Trav's system hydrogen fuel based power system is still there for the other system This makes it easier to intermix Trav-designed ships with B5 craft, but it results in some odd design interpretations from trying to put enough volume of fuel in a craft to work the Traveller way, rather than positing other power sources more in line with what B5's ships appear to be designed around. The system pretty well appears to work (I haven't really had a chance to work with it in detail), but it produces strange looking results, as can be seen with the B5 ships in the book.
Edit: There is a good set of world descriptions included, and the information on the show's characters is quite good and useful.
Finally, there's the physical book itself. The pages have a gray image background that has a very deleterious effect on readability. The sidebars/inset boxes are especially hard to read. This should have been caught on a press check of the book at the latest. Also, the ink is so heavy on the pages that any friction causes black streaks on the page that blot out whatever is underneath. It's hard to read the book for any length of time, and picking out info quick during play is a pain.
The errata pdf includes the same gray image backgrounds on all but the first page, having the same effect on the readability of hardcopy while using up my toner cartridge that much faster.
Edit: The PDF version of the book on DriveThruRG clears away the background. It also includes the errata (though not the free adventure in the errata PDF). This makes the book far nicer!
So, the info is good but not great, and the book itself is an abomination, IMO. I'll appreciate the info for my campaign, but I'll have to transcribe what I use onto a readable medium. Edit: Fixed thanks to the PDF.