You might need to download some extra software to be able to run it on Chromebook but WoW is pretty fun... it's worth doing the 20 level trial account business since you're able to keep your account after it's over and you'll have escaped at least that much of the subscription fees.
The game itself is a bit dry to start with but if you stomach it out a few levels then it can be a lot of fun. Personally, I'm a bit more of a GW2 fan, but WoW has it's own merits.