Most of the books out there seem to be geared toward film rather than TV, though they might be helpful in their discussion of dialogue, character, conflict, etc., since these topics are universal in all writing. Also, a problem with books on TV and screenwriting is that they become outdated quickly; I would want to be reading about Friday Night Lights and House, not Roseanne and Hangin with Mr. Cooper, you know? Books from the 90s also won't be equipped to instruct you on ABC's recent and somewhat overhwhelming six-acts-plus-a-teaser structure. Still, I am of the opinion that it's good to read a variety of books, blogs, scripts, etc. (ALWAYS be reading professional scripts), and take whatever bits of knowledge you find helpful. Here are some books I've enjoyed:
Billion Dollar Kiss focuses not on craft but on the career of TV writing, which makes it a very interesting memoir and a window into what to many of us is a secret world. There are also a lot of fun anecdotes like how Stepakoff initially paid the bills by stuffing envelopes with his pal Kevin Reilly.
Save the Cat is based on the concept that your character has to do something akin to saving a cat so that we like him/her. It's a fun, very specific guide about what should go on every page of your feature. If you're kind of lost in lofty ideas about the Hero's Journey, this is much more practical.
Lofty ideas about the Hero's Journey! Okay, I admit that I never finished Story. I mean, it's frickin thick. (Exactly why it was so helpful in propping open my old rotting window when I lived in Ithaca last summer.) It is pretty classic, though. Maybe just watch Adaptation and take the bits from when Nic Cage goes to McKee's seminar.
I admit I didn't discover this book until I decided I need to stop reading books and start writing scripts...but I love Alex's blog, and I've talked to a number of people who like the book.
The Hollywood Standard is THE book for format. If you're ever thinking, hmm, how do I format an intercut inside a dream sequence that takes place both inside and outside - this is your book! (And PLEASE learn how to do intercuts - I can't tell you how many scripts I've read in which writers put down new slug lines everytime a new person talks in a phone conversation.) Anyway, THS is a good reference guide to have on on your shelf...though I still maintain that you need to read as many professional scripts as possible to really get a handle on format.
I have Desperate Networks at home and I really am going to read it. Our TV Lit Dept head strongly recommends it - so I do too. It's about the modern landscape of television (something you should probably read up on if you're going to work in it).
Feel free to comment with your favorites. (Especially Jamie. How's that?)