It's odd.  I saw the series first.  Took me a while, too - I couldn't get past the title, "The Dresden Files."  My brain kept telling me it was a series about war.  Either that, or an American series set in Germany which seemed just strange.
I finally got round to watching it, and I, too, was underwhelmed.  I like to give things a chance, watch a few episodes before making a judgement.  Well, I watched the whole 12 episodes of this and was still underwhelmed.  Well, that's not quite true - I finished the series feeling very sad that I wouldn't be seeing Murphy or Bob or the various members of the supporting cast again just when it was finding its feet.
Then I read the books - I was cautious and only got the first two to give them a chance.  A few days later I bought another one.  The following day I bought all the other ones I could lay my hands on!  I think it's fair to say that I LOVE the books.  And you know something?  Reading the books has made my appreciation for the series grow.  I know that they're completely different kettles of fish - blonde / brunette; skull / ghost; diplomatically challenged loyal, faithful wizard / smooth, sophisticated (well, relatively), promiscuous (see previous parenthesis) hocky player.  Somehow, though, the love of the books has smoothed over my annoyances with the TV show 'til now I can take each on its own merits.  (Except Paul Blackthorne, who's still a bit dull  phlegmatic.)