Even if they have nothing "spicy", you could browse the world of D&D for various suggestions. You will surely find a lot of inspiration

In particular " Ravenloft Castle" 

The adventure begins with a Paladin who, in a dream, sees a black-haired girl running around the country chased by a bat.
She wakes up and .......... it wasn't a dream

After rescuing her, they venture together to Ravenloft Castle to kill the Castle Lord

Turning a vampire's castle into a world of sex should be simple enough. It is huge from an exploratory point of view, full of secret passages, cruptes, cemeteries and various traps . 

for traps you could use Estrus Mimic as inspiration

There is a passage of the adventure, where you have to sit in an armchair (the reason escapes me). The suggestion lies in
Armchair + Estrus Mimic 

It must be said that this type of books ( Game books), unlike normal ones, have a particularity .

It is made up of seemingly illogical paragraphs but, when you finish a paragraph, you are given a choice to make. Based on your choice, look for the corresponding paragraph and continue the adventure. Specifically: you are at a crossroads and it tells you: Do you want to turn left? go to page ...
Do you want to turn right ?? go to page ...

The events that will follow will be based on the choice made

3 hours ago, Lestat1627 said:

It must be said that this type of books ( Game books), unlike normal ones, have a particularity .

It is made up of seemingly illogical paragraphs but, when you finish a paragraph, you are given a choice to make. Based on your choice, look for the corresponding paragraph and continue the adventure. Specifically: you are at a crossroads and it tells you: Do you want to turn left? go to page ...
Do you want to turn right ?? go to page ...

 

The events that will follow will be based on the choice made

 

 

 

very interested!

I will surely refer to some of your recommendations. 

It is a bit of shame that I haven't read any TRPG books

even though I have been a huge CRPG and JRPG nerd in my whole lifetime.

Thank you!

I read one: The Phantom Tower
She had a detail during the choices. At the fork in the stairs, one goes up, the other goes down
Choose (for example to go down), turn the page and find written: "While you are going up .....". One thinks, I was wrong, I go back and check, no, that's right, I had to go there

The mystery is revealed only at the end.
My sister has been stuck inside for 20 years. She never went out  

Ps : I have a couple in PDF format, they are in Italian

The titles are: The Count Dracula and Frankenstein