Republibot 3.0
Regular
Kevin, as long as you insist on lumping all the books together, your stance that the novels don't count makes some sense. But why do so? The information on what's canon and what's not is freely available so such insistence just doesn't make sense and is kind of like cutting off your own nose to spite your face to discount them. They really enhance the B5 universe.
Jan
Well, JMS himself has said he's pretty displeased with a lot of 'em. I believe there was even a book published a couple years back that listed what counted and what didn't on a book-by-book basis, wasn't there?
Anyway: Right off the bat, we can divide 'em into three batches: The first batch, which sucked excepting for "City of Shadows" and roughly 50% of the Morden book.
The Novelizations, which JMS said contain much that he hasn't decided is canonical or not. (For instance, details Peter David made up)
The Second Batch: These are, on the whole, pretty good, and the first Psicorps book is full-on brilliant. 2nd one, not so much. 3rd one. Meh. Technomate Trilogy was entertaining, but didn't leave me fulfilled. The Centauri Prime trilogy was, I think, the weakest of the batch, but also probably the most 'realistic' in tone.
Then there's the short stories, whcih all count, though a couple of 'em don't make a whole lot of sense. For instance, why would Lyta just throw away a Psicorps warship? She could use it for her own forces, or she could simply go on ISN with it and expose the whole thing.