Wizard subclass

I just made a gnome wizard character and I'm wondering what subclass I should give it. I'm currently thinking of going with Abjuration to make up for wizard's low HP and AC, but I'm also tempted to go with either Divination or Order of Scribes. Which one should I pick?

Well unless you intend to be playing this purely for power think about the story implications of your choice.
An Abjuration Wizard has a focus on protecting things, people and themselves, but also are phenomenal Counterspell/Dispel Magic users. So you maybe you choose this if your gnome is a protective parent or maybe lost someone in their past. Leading them to pick this specialization.
a Divination Wizard focuses on foreseeing the future and seeing unseen things, so your Gnome may be a fortune teller or a paranoid person who wants to be aware of everything around them.
And lastly an Order of Scribes Wizard is the most book focused of wizards, so maybe he was a librarian or has an obsession with gather as much information as possible and writing it down, or maybe he is an avid writer whose stories are so vivid they come to life as magic.

Quote from Firetube >>

Well unless you intend to be playing this purely for power think about the story implications of your choice.
An Abjuration Wizard has a focus on protecting things, people and themselves, but also are phenomenal Counterspell/Dispel Magic users. So you maybe you choose this if your gnome is a protective parent or maybe lost someone in their past. Leading them to pick this specialization.
a Divination Wizard focuses on foreseeing the future and seeing unseen things, so your Gnome may be a fortune teller or a paranoid person who wants to be aware of everything around them.
And lastly an Order of Scribes Wizard is the most book focused of wizards, so maybe he was a librarian or has an obsession with gather as much information as possible and writing it down, or maybe he is an avid writer whose stories are so vivid they come to life as magic.

 My character is a sage, so Order of Scribes would probably be best.

what happened to the Transmuter, Necromancer, Conjurer, etc... subclasses?  In some other book?

I would says try out Illusionist since gnomes are know for their illusions but also has some cool features or a diviner for those sweet portent rolls.

Look at all of the subclasses, and decide which one sounds like you'd have the most FUN with it.