I am new to Pathfinder and just starting to read the very beginning of the core book. One thing that I liked about the introduction text was that they stated that Pathfinder aims to be compatible with existing D&D material (i.e. 3.0/3.5). That's great because I don't yet have the Pathfinder Bestiary, but I do own the pdf copy of The Tome of Horrors and the hardback copies of The Tome of Horrors II and The Tome of Horrors III. So, I immediately thought there should be no problem using them based on the core rulebook assertion of compatibility.
However, now I see that Necromancer Games has published a Tome of Horrors Complete book that is supposedly updated for Pathfinder compatibility. So I find myself scratching my head and wondering why they needed to do this if the original material is already supposed to be compatible?
Can anyone tell me just how compatible the original 3.0/3.5 material is to Pathfinder? What kind of drastic changes should I need to make in the original Tome of Horrors material to use it in my Pathfinder campaign? If there is a place where all this is explained then that would be great.
Thanks.