If you don't care about "Castle," move on.
It's pretty widely acknowledged that "Castle" would not have survived its truncated first season without the brilliance of Nathan Fillion in the title role. But watching the season premier, "Deep in Depth," I was reminded how close "Castle" can come to being fun popcorn entertainment, a la "Burn Notice," before throwing it all away in the next scene.
A lot of the issue with the show so far (and I see a similar problem with "The Mentalist," which I haven't tuned into for a while, so perhaps it's improved) is the lack of real definition for the characters. Any beginner screenwriting course will tell you that a character is more than a backstory and one flaw but clearly "Castle" is riding on the notion that its two leads require only that. Richard Castle-- bestselling writer looking to overcome his writer's block after killing off his hit character is too self-obsessed so that he often puts himself in dangerous situations. Kate Beckett-- upper-middle-class girl whose life took a strange turn when her mother was murdered and is now a cop for the NYPD can no longer give herself over to anyone due to her tragic past. The other two cops (whose names I can't even remember) have nothing. A few quips here and there but no personalities to speak of. Castle's Mom is a diva who gives homespun advice about how to deal with Beckett, whereas the Castle's Daughter is cute and equally enlightened.
This formula works fine for a pilot, even the first few episodes of a season. But by season 2 we should be seeing something deeper in these characters. Instead, "Deep in Depth" works the same beats as every season 1 episode: Castle and Beckett are on the rocks, Beckett saves Castle, Castle and Beckett make up. This is simply not enough.
Another issue is Stana Katic, who plays Kate Beckett. She is simply overmatched in the talent department and it was glaringly obvious in the season premier when she attempted to play a Russian. It was a Brad Pitt as an Italian category catastrophe but the script didn't reflect that at all. In order to have a "Moonlighting"-esque report, Beckett needs to be witty enough to match Castle. It's just not happening.
Lastly, one of the reason the pilot of "Castle" was somewhat succesful was its use of Castle's writerly knowledge. In a perfect world "Castle" would be as grisly as real police work is while utilizing the flights of fancy Castle inherently jumps to. In the pilot Castle stops the wrong man from being put away when he believes the case was too easy-- he wouldn't write a novel with such a dull ending. Unfourtanetly, "Castle" doesn't have any novel approach to procedurals at all and that leaves the show DOA.