ISBN 0590301624 - The only real complaint I've got is that understanding what Bunjee says is a little difficult sometimes - but other than that, great book!
Andy and Karen's father loves to invent things, and his hobby has been pretty harmless so far because nothing has ever worked! This time, Mr. Winsborrow has invented a time machine. When he shows it off for his family, it explodes and his wife is certain that he's finally blown himself to bits. Andy, however, is sure that his father has succeeded and is now stranded in prehistoric times! To rescue their father, Andy and Karen follow his time machine blueprint and manage to get it working. Now all three of them need to find their way home again. Along the way, they have incredible adventures and discover Bunjee, the last of his kind, and a creature so long extinct that no one has ever heard of them. Bunjee can speak and is so excited to find other speaking beings that he doesn't want to be left behind when they finally go home!
Not at all even remotely realistic - and that, in this case, is a very good thing! All budding, young sci-fi fans will enjoy it.