"What will it be about?"
Translation:Wovon wird er handeln?
Not quite, that would be "Worüber wird es sein?", but that sounds a awkward in most cases. "Worum wird es gehen?" isn't as literal, but better. Without context, it's probably a little hard to say anything binding.
So why "wovon" rather than "worüber"? If a conversation is about something, I usually understand it to require the "über" preposition.
Er – der Essay, der Aufsatz, der Vortrag. The constantly recurring problem with personal pronouns and similar words, they appear out of nowhere and are fully interchangable in these examples, but always cause confusion.