
The Crystal Heart Spell is a pony book with an expected launch of April, but people that visit Scholastic bookfairs can pick it up a bit early (usually an elementary school thing). The big thing here is the actual content. While I can't check it here in front of me, the submitter (Sergio) is saying that it is a direct followup to the season finale, though the cover doesn't really hint at that. The expanded synopsis on the back gives a bit of added information:
A royal event has turned Twilight Sparkle's life upside down. To learn how to handle her new status, Twilight goes to Princess Cadance for some guidance. The princess shares her own story about how she came to rule the Crystal Empire and a magic spell that helped her follow her heart. Inspired by Princess Cadance, Twilight Sparkle sets off on a quest for the Crystal Heart Spell!
TwilAUGH (EDIT for people getting here by following links from elsewhere: I'm not the source; everything in the quoteblocks is straight from comments here by richfiles, who got the book from Sergio/BLAMEY0URFATE.)
Tons of SPOILERS posted by a guy who got next month's Expanded Universe Tie-In Novel Twilight Sparkle and the Crystal Heart Spell from the guy who notified Equestria Daily last month that TSatCHS is already available through Scholastic Book Fairs:
Holy horse manure!!!
A "Purple Rain", "The Princess Bride", and "The Twilight Zone" references, Cadance spelled Cadance, And Twilight confirmed to having opulent quarters in Canterlot, but choosing to remain in Ponyville with her friends, all in the FIRST SIX PAGES!!!
Alicorn is defined in the book as "a special breed" that is "able to harness the magical powers of the Unicorns, the flight abilities of the Pegasi, and the strength of a good, true heart of an Earth Pony." Nice confirmation on the way the nature of alicorns reflects all three pony breeds.
Derpy gets an early cameo... Sadly, the Cakes are out of muffins... THE HORROR!!! ◵◠◷
Twilight refers to Cadance as her "Pegasister-in-law" when deciding to head north and visit her.
San Fransiscolt. That is all! XD
You don't have to be a Unicorn to become an Alicorn.
I repeat... You DO NOT need to be a Unicorn to ascend to Alicornhood!
Cadance was an orphaned pegasus, found in the forest and taken in by an Earth Pony village.
The book's writer was obviously privy to official canon information...
Cadance used her special talents for love and compassion to reform a new villain. The villains necklace amplified both their powers. The book specifically refers to Cadance being surrounded by magical energy and taken to a "Strange Place" where she met Celestia and became a princess. Celestia "adopts" her as her niece, and brings her to Canterlot.
Remember, this was written before Magical Mystery Cure was released!
Cadance defines her own destiny to "lead other ponies with my strengths of True Love and Tolerance." Yes, it's capitalized.
Cadance also refers to Twilight: "Of course, my dear new sister", seemingly carrying the idea of alicorns adopting each other as family.
LOLOLOL! Pinkie's Party Time watch is referenced on multiple occasions! What time is it? It's time to PARTY!!!
Gilda AND Trixie leading on and influencing a necklace corrupted Twilight! errmergherd, wat!
Dear God!!! There's book fort reference!!! XD
Interestingly, The writer is privy to the "Strange Place" where Cadance meets Celestia and becomes and Alicorn, but states that the last time all the Mane 6 visited the Crystal Empire was when they held the Crystal Faire and searched for the Crystal Heart to resist King Sombra. This lends credence to the author being specifically made privy to the Alicorn ascension story, and that this was known before the Equestria Games were revealed. It has been said Magical Mystery Cure was written in November of 2011.
The big special moral at the end of the story... "Now I know that a princess is not defined by the things she chooses for her kingdom. All that matters is how she treats other ponies, especially her friends. Princess or not - we are all equal ponies!"
Let that shoot down the "Twilight is above her friends" arguments. This book's writer was clearly given access to inside knowledge to write this book. the fact that it both opens with Twilight choosing her friends in Ponyville over the opulent castle, and her declaring herself an equal to her friends at the end, pretty much shoots those arguments right out of the party canon.

Don't take the Trixie parts too seriously, while she would be loathe to admit it, her part is rather minor (GASP).
This book is clearly written before knowledge of Magic Duel or Games Ponies Play, but given the accuracy of Cadance's ascension, the author was specifically given prior knowledge of The ascension process from Magical Mystery Cure. In general, the book is a one off, but the author was clearly fed knowledge about alicorns that's too specific to be a coincidence. That, and it's appearance just after the season finale, suggests that this was intentionally released as a compliment to the finale.
As for Trixie... She does team up with Gilda to put on a show in the Crystal Empire. She's still telling her "stories" again... Meaning she's being a show mare. Go figure, Twi's friends break it up. Gilda basically tells Twilight that "If she were a princess, she'd do what she wants, and not listen to anyone else". Due to certain elements in the story, this messes Twi up. Gilda mostly acts as the antagonist. Trixie is more in there to be Trixie.
It's obvious that this book was written before Magic Duel or Games Ponies Play, as it misses details pertaining to both of those episodes (namely Trixie's reformation, and the second visit to the Crystal Empire by the Mane 6). Given the uncanny similarity of Cadance's ascension to Twilight's ascension in Magical Mystery Cure though, the author had to have been given prior knowledge of the ascension process from Hasbro. The knowledge this author has about alicorns is far too specific and detailed to be a coincidence. That, and it's appearance just after the season finale, suggests that this was intentionally released as a compliment to the finale, and that Hasbro gave the author detailed advance knowledge of alicorns and their ascension process, to allow this book to be planted as a compliment to the finale.
Actually, there is even the possibility that the author had limited knowledge of Magic Duel. There IS a necklace that is involved in Cadance becoming an Alicorn, but it does not fit the description of the Alicorn Amulet. If there was limited knowledge there, it's entirely possible that the author wrote around "a necklace that can amplify the wearer's power" but filled in some planks themselves. This detail is not known.