Temple of Elemental Evil. You can probably get it as some sort of budget release, or as part of some collection. "(Atari) Action Triple Pack," which also includes Demon Stone and Magic Battlegrounds, might be a cheap alternative. Admittedly, I haven't played the Neverwinter Nights games, but ToEE is very close
to the paper and pen experience. The game carters to your general party alignment and has different endings depending on that, as well as on how well you do.
Having said that, ToEE is one of the "most flawed PoS games" I've ever played. The game itself trudges along without crashing most of the time, but the game world logic falters regularly. Example 1 (spoiler): Later in the game you will need a sledgehammer, among other things. You can complete the game without it, but not perfectly. The sledgehammer is found in two places in the entire game I think, and at the time you find yourself needing it, it may no longer be available (discarded). Joy! Example 2: You can create magic items, but are restricted to whatever masterwork weapons you find. There is no way to commission a particular weapon type, in spite of there being several weaponsmiths around. Example 3: Certain feats are very limited. I picked "Craft Wonderous Items" for my wizard, only to learn that there is exactly one such item in the game that he can craft, and furthermore his alignment prevented him from making that item! Joy! Example 4: You can't use a higher level spell slot for a lower level spell, which is especially annoying with the sorcerer.
ToEE has potential for a great paper and pen replacement, but has so many flaws that it cripples the experience. I understand there is a modding community that has worked out the flaws and bugs and added spells and abilities and raised the level cap and so on. If you choose to try it out (and I think it is worth it), do by all means apply the mods first (they are incompatible with existing save games). This
are probably good ways to get started.
In general, you may like game or dislike it (it's based on a very old module), but this is probably the closest to "paper and pen" you will get in a computer game, and IMO worth a look because of that alone. You may actually come out with a greater understanding of the 3.5 rules than you had before.