how does addiction work?

Super newbie question for I'd say someone with as much xanax as I've taken, but since I've come across the book milk yourself sober (how much addiction dose this remove?), I was wondering how does addiction work with rehab?
1. Does each rehab "amount" stay the same, but every so much rehab done increases rehab cost? or..
2. Does each rehab "amount" make the next rehab increase the "ticks" required?

Just wondering what's the best way to accumulate addiction to use this book, thanks

I am not sure whether this would completely answer your questions. However this is the only guide that I have found on Torn regarding Drug addiction and rehab decay - A guide to rehab decay and addiction - 2021 update

The thread creator seems to address the book and its uses in his original post. Hope this helps

I would say that you should wait and save your book until your rehab bill becomes much more expensive.

Eventually the more you rehab, the more pricey it gets. Meaning when you first start rehabbing and you have -1% addiction (brain icon) you might need $500k to rehab fully. I.e. 2 rehab ticks

As you continue to rehab you will need 4 rehab tick for $1mil and then it will go up as you rehab more. I believe the price of rehab tick ($250,000) should always stay the same unless you have Faction Perks to reduce rehab costs.

For the book, I think you should check out Andymans Guide . This tells you the best way to utilize books.

A final reminder that there is a natural addiction decay that everyone gets a few hours after the new day (essentially a free rehab of sorts), so you should never rehab all the way. Always leave 1 or 2 ticks anytime you rehab, and if you overdose on Xanax to leave a bit more since you can't take Xanax for 24 hours, and that way you will get at least 1 free addiction decay trigger.

Sorry for the long answer, but I hope this helps cover your answer!

Edit: Spelling mistakes

yes that answers my question perfectly thanks