Can ally Galadriel put into play, say, Tome of Atanatar in a mono-Leadership deck?

Oh, I didn't realize that Tome of Atanatar and the other Record attachments are all phrased like "Reduce the cost to PLAY by yadayada", but Galadriel puts into play. So, even independent of other considerations about text on out-of-play cards being active or whatever, I guess the cost reduction doesn't really apply. Same goes for trying to use Galadriel to put a Citadel Plate on Beregond.

Yep. Same thing for A Very Good Tale with cards like Citadel Custodian, Bill the Pony, or secrecy.

The tome doesn't mention ''put into play'', it only mentions the cost reduction effect, so for me, I would even say that Galadriel could play the tome with 1 Leadership hero, because the tome only costs 3, which works with Galadriel ability!

Or... wow.. this is too good to be true and I've never heard of this before... and abusing Sneak attack!!!

The tome says "reduce the cost to play ..."

Galadriel is not playing the card, she's putting it into play.

Therefore, the cost is not reduced and cannot be put into play by Galadriel.

****... It was too good to be true!!