Deus Ex Invisible War is the continuation of the story from Deus Ex. It takes place a number years after JC Denton has joined himself to the AI, Helios. Far from going well, Denton has gone into stasis while he copes with this assimilation. The result is a world left to fend for itself after the collapse. The main theme is based on the socio-political warfare between various governing factions all vying for global control. Eventually, it evolves into revealing the secret motives behind the activities of all these parties. There are several factions involved, most notably the WTO (World Trade Organization), the ORDER, a religious and environmental faction and APOSTLE CORP, a spin-off similar to the Knights Templar. The story begins with the destruction of Chicago by some unknown antagonist and the WTO's reaction to this.
During this time scientists have been working on perfecting the biomods we were introduced to in Deus Ex. Our character Alex D is a recruit of the WTO's academy, Tarsus, and is being prepared for biometric enhancement along with several others. When Chicago is destroyed, these recruits are moved to a Tarsus facility in Seattle. Shortly thereafter, soldiers from the ORDER infiltrate this facility and Alex is directed to escape. On his way out, he picks up and installs his first biomods. From this point on, he will continually be contacted from the leaders of both the WTO and the ORDER and assigned missions. Sometimes these missions are conflicting and he will have to make choices between the two or follow his own counsel. Depending on his decisions, he can remain on fairly good terms with both sides until closer to the end. The game makes no judgment on the ethics of these groups, but leaves it to the player to decide a path.
Biomods come in two forms, either standard or black market, passive or non-passive and each require the right canisters to upgrade them. You can find these, earn these or buy these from other genetically modified beings called Omars. The same applies to weapon modifications and various ammo and tools. Unlike Deus Ex, keycode cards are almost non-existent making the multitool of particular importance, so find as many as you can. Amassing skill points has been replaced in favour of obtaining upgrades through biomods and finding weapon mods. This part of the game has been severely simplified in terms of player interaction, a move even the developers in hindsight consider a mistake.
This type of game where the story is driven to a certain degree by your choices will naturally play out somewhat differently for everyone. Because I chose mostly passive biomods that are always activated, I had very little awareness of them as an interactive feature of the game. Once I had them all upgraded, they just became a part of what my character could do and I rarely had to be conscious of them. However, the canisters are plentiful and you could decide to switch them out to non-passive if you wanted to. This would involve activating them when you needed to. Non-passive biomods also require energy cells, which deplete with use.
In my experience, I found there was just too much of everything. I only ran into a lack of ammo problem once. Ammo is universal, by the way. Other than that, you are just inundated with stuff and monetary credits that end up being fairly useless. I think I had 12 or 14 extra biomod canisters by the last levels as I had no reason to switch my choices. You are also allowed two modifications to any weapon, but these are permanent. However other than a couple of special weapons, the rest are plentiful and you can exchange them with ones you find if you want to change the mods.
Gameplay employs several techniques including role-playing, stealth and shooter. Apparently, it's possibly to get through the game without killing anyone depending on your approach, but as far as I can see, it makes no difference to the possible endings as these can all be decided in the last five minutes.
On the whole, this game will take from its name and become pretty much invisible. It's fairly mediocre and not helped in the least by the difficulty of many in getting it to run in the first place. The only way it would run for me was to update my ATI graphic card drivers to the latest version and disable cores. After that, it periodically crashed to desktop, but not often enough to abandon the game.
To be fair, the game is not too bad till after the Antarctica level, but then it takes a total nose-dive. The developers seemed to run out of steam and the few side missions are like poorly conceived afterthoughts. On Liberty Island, they even use the tactic of spending all your multi-tools on allied bots that don't seem to do anything. This means that you can't open anything to get ammo, which is a cheap shot at attempting to make the game harder. At this point, the story just completely fizzles out.
Replay value might be in trying different biomods and trying different allegiances to see how things turn out, but I suspect it actually won't make much difference in the end. The only real reason I can see for playing this game is if it gives background to Deus Ex 3. The story itself is not bad, but I think my impression was severely clouded by the poor and anti-climatic ending and the game does have its defenders. If you can get it cheap enough, go for it, but don't expect great things. Make sure you research all the issues in running it first though.
Deus Ex: Invisible War was generally well received by critics at release even though its weaknesses were acknowledged. In many ways it was an improvement on Deus Ex. However, the lead designer, Harvey Smith admits that they would have been better served by listening to what the players had really liked about the first game. In trying to reach a broader audience, (read console here) they destroyed the thing that made Deus Ex great and truly made the sequel invisible.
There's even a post mortem by the creative director Harvey Smith on what went wrong with this game if you're interested Post Mortem