Final Doom is a stand-alone huge mission pack based on Doom 2 in 1996. Or more exactly, it consist of two big IWADs, both having 32 levels, both fan-made, both not bringing anything new or changing core gameplay. And both are harder than your average Doom 2. The names of these two level packs are TNT Evilution and Plutonia Experiement.
It also had a PS1 port, which takes only some of Final Doom levels, puts some levels from Master Levels, toned down difficulty and then applied a dark horror-like atmoshpere to it, with low brightness and ambient music. I feel that it's much superior experience for those who aren't complete Doom 2 fans, instead of dragging thorugh 64 levels.
As usual, Steam version was handled in same way as other Steam versions of classic Doom games. That means "badly".
Once again you have to edit "ddraw" line to "opengl" in conf files to make DosBox run without lags. Adn once again setup.exe wasn't included, so you have to manually edit cfg files for controls and music. Yes, uses Soundblaster by default too. At least Steam still gives you option between "classic" and "with mouse" control scheme when launching game.
Specially for Final Doom, configuration isn't the only thing that got screwed up. You see, in Steam version both level packs use same exe file. And that exe is from Plutonia. Not every data is kept in wad file, some were in exe too. What it means is that TNT Evilution uses Plutonia's story for occasional text intermission and it shows Plutonia's level name on same slot on level's automap.
Oh, and they share save slots too. Loading another's pack save crashes the game. You better be careful not to screw up progress by overwriting wrong save is you are beating both packs.
Now, for gameplay of those two packs themselves:
Made me want to yank Chaingunners out of Doom mappers hands, along with their arms. 10/10
Just kidding. Well, at least this common complaint it true for both packs.
TNT Evilution is slightly harder than Doom 2 and is uncertain of what kind of level style it wants to have. It's quite a mix, not exactly all fun one. It can't decide if it wants to have tricky "gotcha" maps, hard crowd stuff, linear layout or confusing mazes. Maps 19 and 20 are really something, as they get out from Doom's abstract style and look like a real place, with office rooms, truck, what looks like actual warehouse boxes processing. It's actually quite nice. And then pack will throw you into huge empty level. So yes, uncertain. It does make use of new textures though, here and there, most memoriable being blood patches on occasional wall. It also includes new music, which helps to give it a personality. They aren't bad either.
Plutonia Experiement is a different beast, that wants to rip you apart. It's more in line with Doom 2 style, only slightly less dull and brown. Mazes are also complex, but in a good way, it doesn't make you run over map in search for a hidden button. It also rarely uses new textures of green color, as well as reuses Doom 1 music. So, in some ways it's a bit better than Doom 2 when it comes to level design. Heck, it even has a map that is maze, filled with archviles that are aware of your existance, hunting you down as you figure out the ways that various doors are opened.
And it's also hard. It's a main point of this IWAD actually, to be hard. And cheap, occasionally, not going to forget situation where I was teleport in front of two teleporting archviles, that you can't break a line of sight from unless you decide to just run away into near pit and try to snipe from down there. So yes, it's very hard, which in PC gaming with saving means abusing quicksaves every few seconds, not the most pleasent grinding.
Multiplayer doesn't seem to be supported by Steam version. You should use Zandronum source port for that. Eh, you will figure it out by yourself.
I actually wanted to not recommend this game at first, since it's kinda more of same Doom 2 but harder, didn't see appeal of playing 60 more freaking levels that hate you. But that was before I properly played it in single-player.
After beating it, I can say that Doom 2 gameplay is still fun, even if using Super Shotgun on everything and having Chaingunner in every room gets repetive. So yes, Doom nuts should get this one.