The Altar of Shulaani Series

Mike was just helping his archaeologist father survey a desert between Egypt and Libya when he fell through an ancient altar and landed thousands of years in the past. The girl he pulled off the sacrificial stone was not human. The creature they befriended eats trees, exists on radiation, and communicates through beeping. The time gates take them from a doomed ancient civilisation to a prehistoric alien world to a rocky island hiding something far stranger than an old ruin. The Galactic Federation keeps classifying them as unclaimed lost property. The Kloogs keep hunting them. And Beeper keeps being right about things before anyone else is. Fast, funny, genuinely strange, and impossible to stop reading. An epic sci-fi fantasy adventure in three parts--filled with telepathic gifts, alien cultures, and a battle for survival on a distant world.