Like all Spiderweb Software titles, Geneforge 5 has amazing gameplay and a really interesting, vivid storyline.
It is really complete as an RPG in every aspect, from character development - class, levelling, equipment and so on - to varied and interesting quests and a lot of significant moral choices.
You can play very much as a single character, or you can raise a little army of different creatures to help you fight. After a while they become like pets - even though you should probably reabsorb them and build stronger ones later on, you can get really attached to your starting creations.
Best of all is how original the storyline is. You don't need to have played any previous Spiderweb games, or even any previous Geneforge ones. Geneforge 5 has a completely stand-alone, original and unique plot. But if you do enjoy this you will almost certainly want to go and play earlier games in the series, as well as Spiderweb's brilliant Avernum series.
Geneforge 5 will give you dozens of hours of gameplay even if you rush through it. And if you take your time - exploring every nook and cranny - you are likely to get well over 100 hours of enjoyment from it. The game is also very replayable as there are so many factions and plotlines, it is really like getting a game and a half, rather than just one game. Whole areas, quests and NPCs will be quite different depending on who your allies are.