When you buy Crosswords you get 3 campaigns. One mini campaign and one with only boss fights. The third (Orcs) basicly 'replaces' the original Ap campaign (although you will still have acces to the original). So as you said it's basicly an Enhanced AP but only Orcs on the march but the other two are brand new(but don't expect them to be as long as AP). One more thing you have access to the new unit right after you get you pet dragon.
Considering new material. Do you remember robber from AP? Give him darker clothes and there you go a Witch hunter. Do you remeber the orcs? Repaint their skin a bit redder and there you go the new blood orcs. Do you remeber the high mage? Give him new clothes and you get the rune mage. Of course every one of these characters get new skills but don't expect to get totaly new monster models. Same model with reskin(like priest(blue) <-> inquisitor(red)).(but i did not met all the new monsters so there could be one or two new stuff too)
Can't tell you anything about the new spells because i haven't found any yet but there are a LOT of new items. About new skills. As far as i know every class get 1 new skills(in orcs camp). I play as a mage and it's new skill reduces the leadership req for every mage user(+ beholders !!
).
Long story short. Am i satisfyed with this game? Yes. Would i rebuy it knowing the content? Yes.
Do i recommend it? Well if you are a huge fan and replayed AP and TL a few times i can recommend it BUT if you expcet a huge difference like The Legend vs. Armored Princess or did not like Ap you can skip it.
My english is crap but i hope you get what i mean.