It was gloriously awesome. How much of the merit goes to Gaiman and how much always belonged to the myth compendium has little bearing in my enjoyment.
The stories are tall tales indeed: huge, fun, magical, gruesome. The characters are as great as flawed: Odin lies, cheats, seduces and steals; Thor is a block-head to which every problem is a nail (hah); and Loki is the charming psychopath. All this is more or less merit of the Edda.
The book is a fast read, very approachable, very engaging, and the order of presentation and building makes it easy to follow the names and elements. The text is cheeky, and has many little asides that had me in stitches, turning wistful and lyrical as we come to the bittersweet end. All this, plus some nuances to the dialogues that made them hilarious (or creepy, or bittersweet), was Gaiman I reckon.
It is a book I want to buy. I want to re-read it, whole and by pieces. Have it as a reference. Read from to my children. Also, as an object, it is a beauty. Full stars.