How Much is "By the Book"

Last week, I read the description of an NPC's death straight from the module. It was the first time I had read anything straight from the book in quite some time, and it was noticeable. I probably should have just summarized it from memory instead of disrupting the "flow" of the game. In any case, someone asked later on in the session how long I had been running a published adventure. The answer to that question is complicated. In some ways, we have all along... but not exactly. I have drawn upon ideas from various modules, but there have been very few sessions that have been "by the book." Here's a quick rundown:

• I started the campaign with a published adventure from Dungeon Magazine, Within the Circle. For the most part, I ran this as written, except I gave Jern more background and made Belig a bugbear.
• I used the dungeon levels from Beneath the Twisted Tower, but I took out all the gibberling nonsense and stuck to monsters that I actually liked.
• I used a modified version of the main map from Perils of the Underdark, the second book from the Night Below adventure/campaign. 
• I borrowed a great deal from Book Three: The Adventure, part of the Menzoberranzan boxed set.
• Everything else has been drawn from the actions/backgrounds of the PCs, or entirely my own design... or hinting at material from a module that just hasn't come up yet.

Of course, it is rare that I run a module as-is, so even if my players found all of these modules ahead of time, I doubt they would have too much of an advantage. Most of them are from 2nd edition so I have had to update the stats to Pathfinder, but that's not where my customization stops. These are some of the changes I make on a regular basis:

• At times, I found it easier to switch a monster to something else entirely rather than update the stats to Pathfinder.
• I like using miniatures, and I will often switch a monster if I don't have a mini to represent it well.
• I create my own battle maps using a combination of Dungeon Tiles and Pathfinder Map Packs. Occasionally, I use one of the larger flip mats. Regardless of what I use for a particular encounter, they almost never match the maps in the module.
• Pretty much anytime I see a monster with an underpowered feat (Deceitful, for example), I swap it for something that helps keep them alive longer in combat... especially since we have a certain dwarf barbarian that likes to charge everything.
• I typically go into optimization mode with "boss" monsters and redo them entirely. When I run the big baddies straight from the book, I am usually disappointed in how challenging they are to the players.
• I've been dropping some clues about a major villain whose plans are in the works, but I'm pretty sure I've been vague enough that none of my players have put all the pieces together thus far. 

And that, I think, should give a little more insight into how much of our campaign has been "by the book."