Secrets of the Nile - The Time Travel Chronicles, #1

If you're reading this, it may mean I don't exist any more. Time travel's like that. Here today, erased tomorrow.16-year-old Madison Bryant is escaping an awkward romance when she leaps into her friend Riley's latest invention--a time machine--as it blasts off on its maiden voyage to Ancient Egypt. Setting down by the Nile in a swirl of sand, the pair plan to stay for a day or two and observe, not interact with anyone.
But when a local girl invites them to her family home, they're drawn into village dramas and can't resist using knowledge from the future to help. An epidemic of dental troubles? Riley introduces toothpaste to the ancient culture. The vizier's teenage son drowning in a hippo-filled river? Maddy rescues him using life-saving techniques acquired on a Sydney beach. Sure, she's read time travel stories with those warnings about not changing the past in case it changes the future in unimaginable ways.
But they don't apply to her. She's just an ordinary girl--a mere speck of sand in the vast desert of time. And nothing she does could ever divert the course of history. Could it? A high-stakes fast-paced journey through the mysterious world of Ancient Egypt.