Modern-Day Man Wins Ragnarok For Aesir

Set in the 1950's-early 60's. Loki (portrayed as smarter and more easily bored than the rest of the Aesir, rather than evil), brings a modern man to Asgard. This fellow (1st name Lief) first prunes the tree of the apples of youth - improving both quality and quantity of the apples, and eventually winning the heart of the tree's guardian goddess. With the aid of the dwarves (who actually do most of the work) he comes up with grenades and a U-235 fission bomb, winning Ragnarok. Read it during the early 60's.

Maybe cast about in Common Knowledge under the Loki section (http://www.librarything.com/character/Loki) or the "Loki" tag (http://www.librarything.com/tag/Loki).

I haven't read it, but Day of the Giants by Lester del Rey seems like a likely match (found by searching for the tag "ragnarok" -- the human character's name is Leif, the time period is correct, and the science-fictional take on mythology seems like sort of thing del Rey would have written. I couldn't find much about the plot online, but there's a teaser here: http://www.shoporium.com/shops/SciFiBuys/view_item.php3?id=186776 (links to a site that's trying to sell it. Sorry.)

There are 40 titles listed here:
http://www.librarything.com/place/Asgard
which might put you on the right trail.

I've read that - I remember about the pruning (and was Freya mad, before she realized the tree was better for the cutting!).

Looks like Day of the Giants is very likely. From Wikipedia's Ragnarok listing -
The Day of the Giants (1959) by Lester del Rey tells the tale of Ragnarok happening in a near future science fiction setting, with an erstwhile engineer arming the Norse Gods with modern weaponry.

Yes, it's Day of the Giants by Lester del Rey. It was originally published as "When the World Tottered" in the December 1950 issue of Fantastic Adventures before being published as a novel in 1959. I only own Day of the Giants, so I don't know what differences there are between the two versions.

Oddly enough, Day of the Giants isn't on the list for Asgard. How would one go about adding it? I didn't see a link on the page.

Which list? I just added Asgard as an Important Place in Common Knowledge for the book (scroll down on the main book page). If you mean tags, someone who has the book cataloged has to tag it.

I was referring to the list with the link from 2wonderY @4.

That list is created from information in the places field in Common Knowledge. Adding Asgard to places for Day of the Giants automatically adds it to the list.

Hah! It's on the list now. And thanks for the information on how things work.

That's it! Thanks - read that one in a small town library as a kid, been looking for it for the last three years.

Yay! Glad you came back now that we found it for you.