there is a book of yaniel in grey garrison, is it an upgrade for the sword?

[SuperbDave]

I didn't bring the sword, but too lazy to reload. can someone pls confirm?

[Martialis]

Book is just background info. The upgrade to Radiance isn't until you meet the dwarf smith Joran in Drezen. As long as you haven't sold it, it doesn't matter if you or another char is holding it or is in your stash, you will get the upgraded version.

[provokastoras]

Radiance upgrades :

if your main is LG when you pick it up it becomes magical immediately (though that might be a downgrade :p) +1
joran in drezen. +2
yaniel when saved in midnight fen holy avenger +4 holy avengers give spellresistance to the whole group when wield by LG characters.
When fighting descari in IZ +6 it actually becomes as strong as Iomedae's own sword there. in my paladin playthrough I still used radiance even though i had both. though you get iomedae's sword for only one encounter.