Hilary Duff is Bubbly Over Her Debut Book

Hilary Duff didn't hold back at The Grove in Hollywood yesterday — she looked just as pleased and proud as anyone debuting their first book would be! Hil smiled her way through interviews and then signed copies of Elixir at the Barnes & Noble, with an outfit change in between appearances.

OK! GALLERY: HILARY DUFF ADDS TWO MORE TO HER RESUME — AUTHOR & TWEETER!

Her big grin spoke volumes about her excitement over becoming a first-time author.

OK! EXCLUSIVE: HILARY DUFF TALKS LIFE AFTER HONEYMOON

Not only has she just embarked on her career as a writer, she's also joined many fellow celebs in starting her Twitter account. The sky's the limit, it seems