Sa'ar: I've liked some of Friedman's work. He had a long run on the TNG comic series -- my favourite is #
46, a terrific standalone story. My main beef with him is that he wrote the same book twice!
Reunion was a murder mystery involving Picard and his former crewmates from the
Stargazer;
Saratoga took Sisko and his old crew and did exactly the same thing. In both cases, a secret involving the death of someone close to Picard/Sisko came out. It was pretty blatant. (You're in good company, though, as Tim Lynch hates Friedman's work too.)
The Trek books as a whole are definitely not up to the shows' standards. They're not much more than licensed fanfic. If you think Wesley is a Mary Sue, you need to read J. M. Dillard's
The Lost Years -- the two original female characters will teach you what Mary Sues REALLY are. The worst of a bad lot is, in my opinion,
Here There Be Dragons. I'm not a John Vornholt fan either, but he may have improved since the ones I've read, as he seems popular now.
There are exceptions to the general mediocrity. My love of Carmen Carter's
The Devil's Heart is on record. The two Dianes (Carey and Duane) don't rock my socks off, but they're always good reading. Dafydd ab Hugh's books are standouts. And the Reeves-Stevens write fanfic, but very, very GOOD fanfic -- the kind that's a great story and a love letter to the show at the same time. (
Yahtzee does this with
Angel.)
I can go either way on Peter David. Comics are his home, and he's a champion there, with countless Marvel and DC titles under his belt. I like his lighthearted stories best (his current Spider-Man title is a desperately-needed breath of fresh air for that character), but almost anything with his name on it is worth checking out. Sci-fi, on the other hand... PAD clearly loves Trek, but he fits it like a bikini fits a sumo wrestler. His books are always funny and often cool (
Vendetta's a classic), but they're not Star Trek books, they're Peter David books. So while I like his writing, I hope he never writes for canon Trek. He serves his own characters much better.
(By the way, I suspect that if I ever wrote Trek books, they'd turn out like that too. I did some stuff in VVS that went way out of character for comedy's sake. It's so tempting to give characters cool or funny lines whose only flaw is that the characters would never say them.)