So I have won! And killed Fane, too.
The Solomonars feel extremely unsatisfying. I think they are one of the few creatures which are neither threats nor interesting at the time when they appear (the rat soldier is boring but OK, you could also think about making Moroi more interesting).
There is something wrong with the Princess. Apparently she casts her Heal spell when there is a wounded man nearby, but she heals herself. And you say she is clever?
I have turned off all the lights in the Library, then used is as a free blood donor station (whenever the vampire got dangerously wounded, she went to the library to get some blood safely, trying not to kill anyone), and was surprised that her spells seemed so weak. Then, I had to finally kill the Princess, and was surprised that I am unable to kill her due to her healing. But she stopped spellcasting once the nearby guy healed naturally.
The fairy was one of the first monsters I met in the pharmacy. I did not know it was her.
I have read the formulae for spellcasting (after winning), apparently the hunger cost is 1+2*level, and the effectivity of the most spells is proportional to 1+level. So higher level spells are less effective per hunger cost. I think this is not right.
After turning off the lights in the Library, I have been using the human form only for the vampire bosses. Sometimes there is not enough food (or not enough soul elixirs) anyway to use the human form much.
I have been investing in Dexterity only. It is of universal use (better defense, attack faster, cast spells faster, run away from the powerful enemies, drink blood before it disappears, remain in the human form longer, creatures have less time to regenerate), while strength is good only for attacking, and intelligence is useful for humans only (maybe you could consider allowing the fourth spell for highly intelligent characters?). I think it is better to outrun Brawlers (and finally even Nobles) as a human than to risk fights.
Thanks again for the very nice game!