I bought the guide books/walkthroughs for RE remake, RE2 & RE3(GC) These walkthroughs were in one guide!, and RE CVX.
I only had these as collectables and because I like reading the documents they have in them such as the bio, weapons, types of monsters, and the history/fact points.
Other than that, I really don't use them because I like to take my time and explore the game the first time. After the first time I start to speed up and already know where everything is at and the passwords/puzzles.
In RE3, there's always a part in which I use the walkthrough for. It's almost at the end, where you have to crack a lock for a door. U have to level the water in the Umbrella Plant. I get confused and just look at the walkthough to just get it right and move on.
I remember when I was playing RE Director's Cut on the PS I got stuck and took me hours to finally find a fix. I had to find the battery for this elevator in the courtyard and try to find the code for that one door in the area where there was a room with a moose head where u get the other stones for the lion head. I didn't use a guidebook because I didn't have access to one back then.