Books Online. Just as the Oracle manuals are required reading, so is SQL’s Books Online.
That said, I recently picked up Ken England’s “Performance Oprimization and Tuning” and found it a VERY useful addition to the Books Online.
Ken Henderson has a couple of good T-SQL books (learn T-SQL… not hard, although a bit of a mental shift from PL/SQL, and I’m sure you’ll agree that, by comparison, T-SQL truly sucks.)
Haven’t come across any good backup/recovery books, and would love to hear from other folks on that.
As for the 1000-page unleashed/black book/etc books… They might give you a bird’s eye view, but IMHO they’re rarely useful as daily references. You may find the occasional nugget of wisdom there.
Better to get a Safari subscription (see, for example, safari.oreilly.com) and browse some of these suckers online.