It's incomplete yet, though. Only general hints and incomplete room descriptions now. I'll be working on it.
As the other guy said, avoid the sacrificial chamber and the kitchen should be avoided at all costs. You may have some fun there, like escaping a bunch of angry cultists just to get into a deathtrap, or getting killed by some harmless keys just lying there waiting for you to pick them up. Try it, but don't overdo it - there's nothing to be gained there. The torture room can indeed be escaped, and it's not only useless, but in fact, if you follow the torturer you will end up on the ground floor, skipping the important cellar stairs location. If you ever find yourself tied up, you have indeed failed because you have missed the important encounter with Shekou. I should also add that the Shaitan room is a loving deathtrap too, because even if you escape, you will proceed immediately to the cellar or to the ground floor but without necessary information. And besides, you get into the wrong part of the cellar this way. Forget about the man in grey - you can meet two men in grey actually (or one man two times?) - the first time, he gives you some useless information and a FEAR point plus a little fight, the second time it's just useless information. Forget about the nurse, too, you can meet her in two places - one place meaning certain death for you, in another one she is just hysteric. Oh, and never drink white wine or eat cheese. Avoid clear liquids in general, too.
The general sequence is: meet Shekou in the Erasmus bedroom, find the hint "Mordana in Abaddon", find Mordana (in the Abaddon room, obviously) and get secret location from her, grab some brandy, fall into a trap to meet Shekou the second time, offer him brandy to get the correct password, go to the bats chamber in the cellar, get under the stairs, use your password, grab the Kris knife, get out of the cellar, get into the Mirror room, grab the box, dive through the mirror, get cast-iron key, get to the dining room, and fight the butler. That's it. You'll need FEAR score of at least 9, because you are going to take 8 unavoidable and nondeductible FEAR points. You don't need LUCK at all, while having high SKILL and/or STAMINA is always nice though not strictly necessary.
Rooms' descriptions follow. The second floor (from left to right).
The Apollyon room. Nice spectral bride leads you here. She tells you a lot of useless but interesting information. Costs you a FEAR point, though. Directions: turn right as you exit the Erasmus room. You may wish to try to escape the bride to have some good fight.
The Erasmus room. Your bedroom where you get to if you managed to not get drugged earlier (which is important). Don't drink the drugged nightcap. Also, feigning sleep costs you a FEAR point, so while the other guy suggests you to do it, I suggest you don't. Oh, and you have to FIGHT the Hunchback.
The Azazel room. You get here if you start from the Erasmus room (which you should) or if you turn right from the Mephisto room after you have got tied up. You can investigate only one of the three things here so choose careful. The cupboards here cost you some FEAR, so avoid them. The drawers contain a WEAPON, but you can get another very soon and you won't have necessary fights until then. The vials are: shielding potion (yellow), harmless useless liquid (green), deadly poison (red), weakening poison (white).
The Mephisto room. Next to the left of the Azazel room. This is where careless guests end up (including yourself, yes). That's why you find a rope and a shattered glass here. The rope is useless, and so is the whole room.
The Balthus room. Next to the left. Contains a zombie to fight and to key to get out. You can't get out without a fight and some FEAR points. So yes, it is useless also.
The Diabolus room. Behind the unmarked door next to the left of the Balthus room. You may restore some STAMINA here at the expense of some FEAR (more if you stay, less if run away). Not worth it, if you ask me. However, if you just walk past this room to the window you will get the important "Mordana in Abaddon" message.
The storeroom. On the second floor as the landing bends right. After the unmarked "Mordana in Abaddon" door. Some garlic here may be useful if you wish to visit the Shaitan room for some entertainment. Also, a WEAPON here, this one you should really get.
After the storeroom things get really weird. If you go through the back door, you have the Mammon and the Shaitan room waiting for you. If you enter the Shaitan one, there is no going back. But if you enter the Mammon room and leave it, you can follow the landing past the Tuttivillus room (272). On the other hand, if you leave the storeroom immediately or go through the back door and immediately go back, you get the opportunity to enter some unmarked door (233) and then (374) turn to some passage (339) containing Asmodeus and Eblis rooms which are unavailable for some reason if you decide to explore the back door of the storeroom (where the Mammon and Shaitan rooms are) and then go back. I'll try to map it out later. But let's go on with the descriptions.
The unmarked door next to the storeroom (if you go back to the landing) is not even a room. Just some fun FEAR points.
The Eblis room (125). At best, you can get out of here alive loosing or gaining nothing. Or you may end up in the cellar without necessary information to keep yourself alive.
The Asmodeus room (154). The man in gray, your only ally in this goddamn place! It is just the only thing he actually gives you is one FEAR point at best. Or loose some stamina if you are not skillful enough.
The unmarked door near the Belial and the Abaddon rooms. Some free STAMINA points and some FEARFUL fight if you want one.
The Belial room. Get some rest if you wish. One FEAR point, though, which you may deduce right away if you are careful with your choice. That is, if that one point didn't frighten you to death already.
The Abaddon room. Obviously, Mordana is here. However, waking her up costs you some FEAR points since she is dead. More or less points, depending on the chosen way to wake her up. And some FIGHT here.
The first floor (from the front door deeper into the house).
The front door. Some fun FEAR points.
The drawing room. The brandy (necessary to win). The fire sprites guarding the trap (necessary too). The fight with them can be avoided, but is not fatal.
The study. Some death, FEAR and a dangerous item. Oh, and a (useless) secret passage to the cellar too.
The mirror room. You have to get here to get the key to the dining room, but only when you have the ultimate weapon (Kris knife). Otherwise you are dead.
The kitchen. A very fun place. Try to get yourself killed in a fight, or get hurt by some keys, then get captured by the evil guys. You are dead as soon as you enter this place.
The dining room. You cannot get here without the cast-iron key and if you don't have one, you are dead because you have to go to the kitchen. And if you have the key, then you are dead anyway unless you have the ultimate weapon, because this is the place where you fight the final boss.
The cellar. A very nice place. The only place you want to visit here is where the bats attack you, which gives you a FEAR point. You may fight here, though it is not necessary. And of course, the secret door is located under the stairs. You need to know how to locate it, and the password to open it. All other places you can get to are mostly deadly.
The cells. You can get here either by falling into a trap in the Eblis room or by following the secret passage from the study or by falling into a trap in the drawing room (the correct way). You are allowed to talk to exactly one person here. One of them will kill you, though. Now this is the funnest place in the whole book! I mean, that man killing you so his jailers won't know about him getting a weapon. Now just imagine that. "Hey guys, your helpless prisoner here! Are you bringing us our meal? Ah, that's so kind of you. No, no never mind that bleeding corpse here, he has just... you know... just dropped here dead and started bleeding for some reason... or maybe for no reason at all, how could I know? As for me, I'm completely harmless, yes". Isn't that hilarious?
The torture chamber. You get here from the cells. Can be escaped if you know enough words. Not too many, actually. Knowing Drumer, Mordana, Kelnor, Shekou and Abaddon is pretty much enough. Or just choose your way to die here - there are whole two choices!
The bats chamber. You get here by walking past torture chamber. Here are the stairs under which the secret door is located. You can also fight the bats if you wish, but it's not necessary.
The sacrificial chamber. You get here by following the stairs from the Shaitan room or from the mirror room and turning left afterwards. You can get away from here either if you are lucky, or if you have got the pentacle. However, this leads you into a place with two rooms, both of them contain either death or nothing useful, depending on your choices and stats. And there are no ways out. So you are dead no matter what.
The food store. You get here by following the stairs from the Shaitan room or from the mirror room and turning right afterwards. Some food is here. The cheese and the white wine are obviously poisoned. Everything else just restores your STAMINA which doesn't matter much because you are dead if you got there.
The door opposite the food store. A prisoner is here. You may make him your ally, which will only kill him very soon. Again, if you are here you are dead.
The cultists' dressing room. One more place to choose your way to die. Don't remember how to get here, though. I'll fill it later.