Before you even think about seeing "Love Never Dies" - there are a few things you will need to be wary of. First off: I hope you have a pinch of salt with you as you'll certainly need it in every aspect of this musical.
To summarise - we are supposed to believe that at some point, between the Phantom's beautifully tragic "Christine, I love you" in the finale of "POTO" and Christine and Raoul's wedding, she (Christine) managed to find the Phantom - despite him living in the Opera House for most of his life and never being found - and we are supposed to believe that they had sex. The next morning, while Christine slept, he ran away out of shame and she went back home to Raoul.
We are also supposed to believe that Madame Giry, after betraying the Phantom in "POTO" and telling Raoul how to find his lair, suddenly has a change of heart and decides she will help him again. She uses Meg Giry (remember her sweet little daughter, Christine's best friend?) to help secure finances for their departure to Coney Island. Yes, Meg Giry became a prostitute and in "Love Never Dies" is an 'Ooh Lah Lah Girl'.
One last thing that we need to believe is that Raoul, the love of Christine's life, turned into a nasty, drunk gambler who lost all their money.
So, knowing that, we can now proceed with the musical. I would recommend that you see the West End version (as opposed to the more widely available Australian one) as it features Ramin Karimloo as the Phantom - an excellent performer in this role and Sierra Boggess as Christine.
Aside the very questionable plot, this musical is spectacular. The music is easily the best thing Webber has written since "POTO".
Some notable songs are:
"The Beauty Underneath" in which the Phantom takes Christine's son, Gustav, on a tour around Coney Island. This song is laden with electric guitars and excitement as it continues to build up in a frenzy of both the Phantom and Gustav's awe until the climax where the Phantom removes his mask to reveal his face.
"Dear Old Friend" is sung when Raoul and Christine bump into Madame Giry and Meg backstage and showcases one of Webber's greatest compositional strengths: pitching several voices against each other. However, this is different in that all 4 of them have different emotions which are apparent behind the false front of being happy to see your 'dear old friend'.
"Love Never Dies" is the title track. It is a beautiful performance by Christine and is dripping with heartbreak as she chooses the Phantom over Raoul.
I would definitely recommend you give "Love Never Dies" a try if you think it'd be possible not to take it too seriously as a follow up to "POTO". The aesthetics of the Phantom's show on Coney Island are phenomenal and the music more than compensates for the poorly thought out plot (which has been described as poor fanfiction as opposed to an actual sequel).
I dislike musicals and I dislike Andrew Lloyd Webber - I only watched this as it was a continuation of "Phantom Of The Opera and I still found it brilliant.