Which is to say, even official lore isn't canon. ;)

@Artificial: Well, the thing about the RPG sourcebooks is that they were obviously given documents and tons information from Blizzard, and a lot of stuff was fleshed out that later appeared in the game, such as the zones of Northrend, the Elemental Planes, the history of the goblins, and so on. However, Blizzard is constantly revising their ideas, pretty much right up until release. This means that pretty much any way you slice it, stuff introduced via the RPG is, at best, tentative.

That said, you can pretty much immediately throw out the campaign story hooks and any d20 conversion aids, such as all the monsters in Appendix III of the Monster Manual. Although a lot of information and art came from Blizzard, Whitewolf did a lot of stuff on their own, too.

Note also that the RPG line has been canceled for a while now, so we probably won't be seeing any more sourcebooks.

Hey, are you Hungarian? The link you posted about the WoW RPG book was from the Hungarian WoWWiki