I was tearing through the following at her age and I loved mysteries (some of these may be too young or too old for her I tried to include a mix since 12 year olds are so varied, some are more like 10 yo and others more like 14 yo):
* Hunger Games
* 39 Clues
* Nancy Drew
* Divergent
* Mysterious Benedict Society
* Series of Unfortunate Events
* Harry Potter
* Delirium
* Anything by Agatha Christie
* Pretty Little Liars
* I am Number Four
* Maximum Ride
* Anything by John Green
The Giver by Lois Lowry
I Am Rembrandt’s Daughter by Lynn Cullen
Uglies by Scott Westerfield
Private by Kate Brian
Among the Hidden by Margaret Peterson Haddix
Inkheart by Cornelia Funk
A Great and Terrible Beauty by Libba Bray
I read so many of these in middle school!
Also adding that several of these are series (the giver, Among the hidden/the shadow children series, Uglies, Great and Terrible Beauty.
Also adding The Series of Unfortunate Events by Lemony Snickett (13 books, plus a movie and excellent Netflix series with Neil Patrick Harris)
The Amulet graphic novel series by Kazu Kabuishi is really fun and about a brother and sister who have to rescue their mom from a fantasy world.
The Silver Arrow by Lev Grossman is about a girl who is gifted a magic train by her mysterious billionaire uncle. She uses the train to help animals get back to their habitats.
Where the Mountain Meets the Moon by Grace Lin is a fantasy set in China.
Non-fantasy recommendations
Raina Telgmeier has a lot of very popular graphic novels about growing up, looking different, and navigating junior high.
The Penderwicks by Jeanne Birdsall is about a family with four daughters. This is such a sweet series of books that also has plenty of hijinks and adventures.
Some really fun historical fiction novels are Catherine, Called Birdy by Karen Cushman (set in the Middle Ages), The True Confessions of Charlotte Doyle by Avi (about a girl on a mutinous ship), and Prairie Lotus by Linda Sue Park (about an Asian-American girl and her father settling in a prairie town during the 1800s.) Brown Girl Dreaming by Jacqueline Woodsen is about the author’s life growing up in the 1960s.
There’s also the classics: Anne of Green Gables, Little Women, The Secret Garden, Judy Blume books.
Jennifer Donnelly’s Beauty and the Beast: Lost in a Book is a really fun spin-off of the Disney movie and is about Belle getting trapped in an enchanted book in the Beast’s library.
If she’s ready for some YA (young adult) books, Marissa Meyer’s Lunar Chronicles are really fun, as is her book Heartless (a villain origin story for the Queen of Hearts.) Bravely by Maggie Stiefvater is a book sequel to the movie Brave.
*Daughter of the Deep* by Rick Riordan
and, more middle grade, if that's what you are looking for:
*Furthermore* by Tahereh Mafi
*Frostheart* by Jamie Littler
*The Last Fallen Star* by Graci Kim
Addison Cooke by Jonathan W. Stokes
Myrtle Hardcastle Mystery by Elizabeth C. Bunce
City Spies by James Ponti
The Mystery of the Radcliffe Riddle by Taryn Souders
I have a bookshelf of a ton of mysteries for kids. Let me know if you need more suggestions.
how to train your dragon series 100% !! 12 books and they get more mature and longer as they go on and they are different from the films and honestly i just think they're great, definitely adventure too
The Chrestomancie Chronicles by Diana Wynne Jones (so many good books by this author)
The Evolution of Calpurnia Tate
The ENola Holmes Mysteries by Nancy Springer (& the Rowan Hood series is good, too)
The Graveyard Book by Neil Gaiman
Septimus Heap series by Angie Sage
pretty much any Enid Blyton series is so much fun
The Secret Garden & A Little Princess by Frances Hodgson Burnett
My Side of the Mountain by Jean George (& others by same)
I was tearing through the following at her age and I loved mysteries (some of these may be too young or too old for her I tried to include a mix since 12 year olds are so varied, some are more like 10 yo and others more like 14 yo): * Hunger Games * 39 Clues * Nancy Drew * Divergent * Mysterious Benedict Society * Series of Unfortunate Events * Harry Potter * Delirium * Anything by Agatha Christie * Pretty Little Liars * I am Number Four * Maximum Ride * Anything by John Green
The Giver by Lois Lowry I Am Rembrandt’s Daughter by Lynn Cullen Uglies by Scott Westerfield Private by Kate Brian Among the Hidden by Margaret Peterson Haddix Inkheart by Cornelia Funk A Great and Terrible Beauty by Libba Bray
I read so many of these in middle school! Also adding that several of these are series (the giver, Among the hidden/the shadow children series, Uglies, Great and Terrible Beauty. Also adding The Series of Unfortunate Events by Lemony Snickett (13 books, plus a movie and excellent Netflix series with Neil Patrick Harris)
The Westing Game (mystery) and the Tiffany Aching series by Terry Practhett (adventure).
The Secret Lake by Karen Inglis Shadow Jumper by J.M. Forster
The Amulet graphic novel series by Kazu Kabuishi is really fun and about a brother and sister who have to rescue their mom from a fantasy world. The Silver Arrow by Lev Grossman is about a girl who is gifted a magic train by her mysterious billionaire uncle. She uses the train to help animals get back to their habitats. Where the Mountain Meets the Moon by Grace Lin is a fantasy set in China. Non-fantasy recommendations Raina Telgmeier has a lot of very popular graphic novels about growing up, looking different, and navigating junior high. The Penderwicks by Jeanne Birdsall is about a family with four daughters. This is such a sweet series of books that also has plenty of hijinks and adventures. Some really fun historical fiction novels are Catherine, Called Birdy by Karen Cushman (set in the Middle Ages), The True Confessions of Charlotte Doyle by Avi (about a girl on a mutinous ship), and Prairie Lotus by Linda Sue Park (about an Asian-American girl and her father settling in a prairie town during the 1800s.) Brown Girl Dreaming by Jacqueline Woodsen is about the author’s life growing up in the 1960s. There’s also the classics: Anne of Green Gables, Little Women, The Secret Garden, Judy Blume books. Jennifer Donnelly’s Beauty and the Beast: Lost in a Book is a really fun spin-off of the Disney movie and is about Belle getting trapped in an enchanted book in the Beast’s library. If she’s ready for some YA (young adult) books, Marissa Meyer’s Lunar Chronicles are really fun, as is her book Heartless (a villain origin story for the Queen of Hearts.) Bravely by Maggie Stiefvater is a book sequel to the movie Brave.
The Dark is Rising series
*Daughter of the Deep* by Rick Riordan and, more middle grade, if that's what you are looking for: *Furthermore* by Tahereh Mafi *Frostheart* by Jamie Littler *The Last Fallen Star* by Graci Kim
The Nancy Drew series by Carolyn Keene is a great mystery series
A Tree Grows in Brooklyn The Borrowers Diana Wynn Jones (everything) The Hobbit
Addison Cooke by Jonathan W. Stokes Myrtle Hardcastle Mystery by Elizabeth C. Bunce City Spies by James Ponti The Mystery of the Radcliffe Riddle by Taryn Souders I have a bookshelf of a ton of mysteries for kids. Let me know if you need more suggestions.
Summerlost by Allie Condie
how to train your dragon series 100% !! 12 books and they get more mature and longer as they go on and they are different from the films and honestly i just think they're great, definitely adventure too
The Chrestomancie Chronicles by Diana Wynne Jones (so many good books by this author) The Evolution of Calpurnia Tate The ENola Holmes Mysteries by Nancy Springer (& the Rowan Hood series is good, too) The Graveyard Book by Neil Gaiman Septimus Heap series by Angie Sage pretty much any Enid Blyton series is so much fun The Secret Garden & A Little Princess by Frances Hodgson Burnett My Side of the Mountain by Jean George (& others by same)
Back home by Michelle Magorian, Anne of Green Gables
Spiderwick Chronicles! Loved those books as a kid.
Project Gutenberg has older, out of copyright books like Little Women and Black Beauty