Is the Campania Express up and running again?
Much faster than Circumvesuviana?

Will be staying in Pompei, but hope to visit Herculaneum and have dinner in Sorrento.
Is there a time table for when last train departs Sorrento in the evening?

For Pompeii to Sorrento, you would only save about 10-15 minutes over the regular train and it costs far more. On Pompeii to Ercolano Scavi, you aren't really saving any time (3-4 minutes?).

No, it doesn't run as late as the Circumvesuviana or anywhere near as often.

Is your hotel in Pompeii even close to the Circumvesuviana Pompeii Scavi station or is it near the Trenitalia Pompei stations (Trenitalia does not go to Sorrento or Herculaneum)?

The Campania Express began running again in 2017 on April 15th, and is supposed to continue until October 15th.

http://www.napolidavivere.it/2017/04...ei-e-sorrento/

It looks as though the last departure from Sorrento is at 9 PM. That probably would be too early for a dinner in Sorrento.

The Circumvesuviana runs much later, but the schedule varies by the day of the week. (It's a commuter train, after all.) You can check the schedule for your dates here:

http://www.eavsrl.it/web/orario-integrato

I think the boxes are easy to figure out, but "da" is "from"; "a" is "to"; "data" is "date"; and "ora" is "hour". They will show a number of trains leaving after the specified hour.

The Circumvesuviana takes half an hour from Sorrento to Pompei. The Campania Express takes almost as long, probably because there is no additional track that would allow the trains to overtake slower trains. It also costs considerably more, so I think the only reason to use it is to avoid the commuter crowds.

Campania Express is seasonal and runs from 4/15/17 to 10/15/17.

Circumvesviana is year round (every 30 minutes until and runs later in summer than the rest of the year).

A tidbit for the curious: The modern city is called Pompei, whereas the ancient city is Pompeii.