totally agree with most of what's been said.
Personally, I like Marino's The ICU Book, but beware, some attendings hate it! For surgery Surgical Critical Care by Abrams is good BUT 3x as expensive and way more dense... probably better though...
I'd still spend the $50 on The ICU Book... it's been pretty good so far, or I just don't knwo the mistakes -- which is always scary!!!