I am buying the game for the single player mode. Is it fun?

Yes. It's a classic.

This is one of my favorites. The action is good, the maps are large, and the story is told mostly from logs you find during your journey (no cutscenes). Levels follow sensibly from each other in a believable way instead of going from neat map to neat map. There's a lot of environment variety.

Unreal's AI coder is the same guy who made the famous 'Reaper' bot for Quake. Most enemies won't just stand still and let you kill them. Some are very good at dodging your non-instahit weapons. You'll have to overwhelm, trick or surprise them. That may or may not appeal to you. Three such opponents are very dangerous. As such, encounters tend to be smaller than other fps, but not always (recalling some of the end game stuff).

Yeah, the AI of some of the monsters, notably the Skarj, was extremely good.
About the level design, one weakness is that each level is self contained and you can't go back to previous levles.

The single player is simply amazing. Some of the areas admittedly stumped me, thus giving me a challenge to sit on for about a week (I'm a horrid puzzler, always have been). The AI is some of the best I've seen (the Skaarj are fierce as they should be!), and the weapons never cease to amaze with blowing apart your next enemy. I can definitely recommend it, played it as a kid, played it last year, will play it again in the very near future!

I found the first 20% of the maps a bit repetitive, and the Nali writings about mundane things were a bit silly. But after that I found that the game offered distinct and complex environments that span multiple maps. The monsters also became much more diverse. It came as a pleasant surprise that some of them could carry and utilize same weapons as you.
I didn't really like the random secret rooms, though.

I missed the game the first time around (I don't think my PC was up to par in '98), and I'm enjoying it so far. It definitely holds up well to its competitors. I like it a lot better than Half-Life, which feels constrictive in design by comparison.

Classic. I have this tradition where I run through the game in a day.

One of my favourite shooters. Does this tradition also include lots of coffee and MREs? :)

I think the level design in Unreal is sort of inconsistent. That being said, it's my favorite single player FPS.

It is one of the primordial FPS games. It has great plot,if you're inclined to ferret it out from all of the translator logs you find throughout the game,and the gameplay is smooth as silk,which is better than can be said about most modern games of ANY stripe. Level design is amazing,combining both ambiance and function,and the weapons feel RIGHT.

Speaking of weapons,they are the star if the show in the game. Every weapon has at lest two firing modes,be it something mundane,like the AutoMag firing faster with less accuracy (Gangsta style!),to the outlandish,like manually guiding the flight of a razor blade. Some even have more than two firing modes. I'll leave those for you to discover,though.

Enjoy the game. I know I do. Try not to kill yourself with your own flak cannon.

Yeah, I liked it too. Personally I prefer QUAKE II, but it's a solid experience anyway. Plenty of decent weapons and smart enemies to keep you on your toes. I found the level design a little odd at first, but once you figure out the patterns you shouldn't have any problem. Just remember to read the audio logs and translate the signs on the walls!

Overall a very enjoyable shooter with a surprisingly good story. I know this is a late reply but just wanted to say that it's well worth buying to anyone who is reading this!

I loved it when the game was released, and still loved it recently when I finished the GOG version. The only thing I dont like is the "Return to Na Pali" expansion.