Maskerade by Terry Pratchett

The story begins with Agnes Nitt leaving Lancre to seek a career at the Opera House in Ankh-Morpork. When Granny Weatherwax realizes Nanny Ogg has written an immensely popular cookbook but has not been paid by the publisher, the witches also leave for Ankh-Morpork to collect the money, as well as to attempt to recruit Agnes into their coven, to replace Magrat Garlick who left the coven when she became Queen of Lancre (in Lords and Ladies). This has the side benefit of distracting Granny from becoming obsessive and self-centered, or so Nanny believes to her great relief. Agnes Nitt is chosen as a member of the chorus, where she meets Christine, a more popular but less talented girl. The Opera House Ghost, who has long haunted the opera house without much incident, begins to commit seemingly random murders staged as "accidents", and also requests that Christine be given lead roles in several upcoming productions. Due to her incredibly powerful and versatile voice, Agnes is asked to sing the parts from the background, unbeknownst to Christine or the audience. Having discovered the problems at the opera house and also having coerced the publisher to pay Nanny richly for her book, the witches investigate the mystery, with Granny posing as a rich patron, and Nanny insinuating herself into the opera house staff. Agnes unmasks Walter Plinge, the janitor, as the ghost, though as he is seemingly harmless, the others are unconvinced. Another employee is suspected, but turns out to be a member of the Cable Street Particulars. The witches determine that the finances of the Opera House, which are a complete mess, have been made so intentionally in order to hide the fact that money is being stolen, with the murders being used either as a distraction or to cover evidence. It is finally revealed that two people had been masquerading as the ghost. The original (and harmless) ghost, Walter Plinge, was being psychologically manipulated by the second ghost, who assumed the identity to commit the murders and theft. With the witches' help, Walter is able to overcome his fears and help defeat the murderer. - Wikipedia.

The witches sub-series of Discworld is always entertaining. I can't think of one of the five I don't care for. This is the subseries where Pratchett seems to have the most fun spoofing other classic works: Shakespeare, fairy tales and, with this and Carpe Jugulum, classic gothic horror novels (Phantom of the Opera and Dracula).

I am especially fond of this and Carpe Jugulum because of Agnes. Susan and Tiffany were wonderful young leading ladies but I really longed for more Agnes. The split in her mind with her alter-ego Perdita is incredibly relatable. If you feel that what you're expected to be (the good girl, the capable one) doesn't always fit with what you really feel you are or could be, then you get it. We are not always at our best when we're on our best behavior, and this is well illustrated with Agnes. Perdita is Agnes' daring, bitchy, glamorous side coming out, and who knows what Agnes could achieve if she didn't behave all of the time?

There's a common theme in the Discworld books of talented young outsiders who are looking for their place in the world. With her supernatural singing ability, Agnes hopes to find a future on stage, or at least out of small-town Lancre where her choices are limited to wife or witch. It takes the events of the this book, plus “meddling” on the part of Nanny Ogg and Granny Weatherwax for her to get the idea that the stage, and the shallow life of showbiz where usually the thin and pretty are favored, might be limiting and not enough for someone as talented as Agnes.

Throughout Maskerade is (of course) the theme of masking your true identity. The most obvious case is Henry Slugg, a very Ankh-Morporkian singer who pretends to be foreign-born Sr. Basilica. Granny Weatherwax gets in on the act, pretending to be a grand lady in order to infiltrate the Ghosts Box at the Opera. Walter Plinge and Agnes are the most interesting/least shallow of these masked identities and they both suffer in roles that the world has placed on them.
“You want to be something else and you're stuck with what you are,” said Agnes “I know all about that. You're lucky. All you have to do is put on a mask...”

Walter masquerades as a simpleminded handyman who works in the opera house. It's slowly revealed that there might be much more to him. The central mystery of Maskerade is whether or not what he's repressing is a personality capable of multiple murders.

There are other things to love about Maskerade.

1. The humor is dead funny: dark, cynical, silly, sarcastic, slapstick, as well as fun cameos from other Ankh Morpork regulars.

2. A heroic fantasy story with older women as the heroes seems to be a rare thing. Nanny Ogg gets to shine here, her social skills and ability to win other people's trust are indispensable and even Granny admits that it's a kind of magic that she never excelled at. Nanny is more than just Granny's sidekick and balancing force. Part of the power of the old witches is that they know themselves very well and have all the confidence that comes with that. In contrast, they don't spend time doubting their identity. (“-Oh yes? Can you identify yourself?
-Certainly. I'd know me anywhere.”)

3. Even if you're not big on opera, this book would probably appeal to theater kids, which I was. The backstage excitement, rehearsals, “show must go on” , the professional jealousy, it's all a part of the fun and very well portrayed here. (I can see bits of my old self in Agnes and Christina.)

The literary parody and Scooby-doo style mystery might seem a bit silly superficially but there's so much good stuff here.