Damn, pretty addictive game. took me a couple of hours but I manage to get to the ending. The learning curve can be summed in knowing when to use the books and what strat to use depending in the units you get at the start (Usually the ones you can pair in 3es so you can level them up). Summoner strat seems to be the easiest.
Level 3 curse book and level 3 summoner book combo pretty well when you dont know if your lane will survive or you are agaisnt high health enemies and you lack sucubus.
If you are lucky with mausoleum you have an almost secure win.Lastly you pretty much can ignore the princes if you have more than 2 health or if you know you can kill the king before they manage to get to the last tile.