I am thinking about getting From the Grave for my group since a player wants to be a Necromancer, however his conscern is that it appears to have only 1 follower option that being the Ghoul.

Is there other options (skeletons or Zombies) and can you only have 1 undead at a time or a small force of undead?

Thanks

There is at least one raise dead spell with which you can get skeletons and zombies. The ghoul is more permanent though and has more abilities tied to it.