Emma:

Wants Jeff Matthews to notice her.
Hates sexist boys.
Wonders when she’ll get her period.

Tom:

Must avoid looking like a wuss.
Must deal with his blended family.
Must get a chance with Kelly A.

Then something freaky happens: Emma and Tom switch bodies. And until they can find a remedy:

Emma:

Can’t believe she has a thingie.
Hates mean girls.
Finds out secondhand that her period has arrived.

Tom:

Must learn to put on a bra.
Must deal with an overachieving family.
Must not be alone with Jeff Matthews.

From the Hardcover edition.