Ian Fleming got into a habit early on in his career as a novelist. He would churn out one Bond novel a year, during the summer, at his Goldeneye estate in Jamaica. This kind of routine can be deadening when one writes without inspiration, and, unfortunately, that's what apparently happened when he wrote "Goldfinger."
This isn't a bad novel, but compared with the better Bond books, this is pretty weak. The plot seems hastily assembled, is far-fetched, and the ending seems rushed and improbable, even for Fleming.
That said, it does have its good points. The villain, Auric Goldfinger, is one of the most fully realized characters Fleming ever created, and Oddjob is certainly a menacing strongman. The early chapters, where Bond teaches Goldfinger a lesson and then trails him across Europe, are mostly good, but the golf game goes on WAY too long and seems indicative of Fleming's general lack of ideas here. The last several chapters are a mess; the whole idea of robbing Fort Knox wasn't that great to begin with.
All in all, "Goldfinger" is little more than a mediocre addition to the Bond series.