Master Excel VBA
I don't recommend books very often... lord knows I simply don't read that many either :-/
But I often get asked my opinion about books on Office development and so I thumb through enough of them to know the good vs. the bad.
That said, if you are looking for a good book on Excel VBA and you want one that has a nice fluid tone aimed at a dignified reader knowledge level, allow me to point you at Excel 2003 Programming with VBA.
It's written by Steve Hansen of the Dakota Technology Group whom I know from years past (and present). Now before you jump me and say "Ah... friend refrerral... I smell a credibility leak...", let me say I wouldn't waste my time typing this out if I didn't think this is a good book.
He approaches the subject (one of my favorite topics btw) in a way I would have done so if I was writing on it. As I looked at his book, it reminded me of a conversation between two tech friends/co-workers, where one was inspiring another to go deeper into Excel development and was offering up personal advice on approaching it... I could almost hear Steve talking over the cubicle walls as I read thru it...
So if you're in the market, this book is a winner. Need more proof? Check out a sample chapter here....