Simon vs. the Homo Sapiens Agenda by Becky Albertalli (Penguin Books, 7 April 2015)
SIMON VS. THE HOMO SAPIENS AGENDA is a burst of sunshine in book form, and you need its happiness in your life. Trust me.
Simon is sixteen and gay and a lover of Oreos. He's been emailing this guy anonymously – he only knows this guy as 'Blue', and he knows that Blue is also gay and goes to the same high school as he does. Neither of them are out and, despite only being able to communicate by emailing each other using secret identities, they're slowly falling in love anyway. But everything goes haywire when one day, Simon accidentally forgets to log out of his email while in the school library. His classmate Martin Addison reads them and decides to blackmail Simon into helping him get closer to Abby, one of Simon's friends.