Return to the Lost World:

Return to the Lost World: A Luke Challenger Adventure by: Steve Barlow and Steve Skidmore
Fiction: Children's, Mystery, Sci-Fi,  Classics, 329 pages
Physical Book Count:3
Book Count:11

This book is first in a series.  It takes place a few decades after the book "The Lost World"  by: Sir Arthur Conan Doyle and features the grandson of the man character of the original story and his cousin.  Their family is now leaders of innovative equipment design that is used by England, America, and other countries in the time between the two world wars.  Luke, the main character, is a teen as is his cousin Nick.  They made their own flyer and enter it into a competition.  While in the competition Luke is almost killed by another pilot, a German Nazi with a mysterious tattoo of a snake coiled around a spear.   
When they get back to England they find out that Luke's mother, a paleontologist, has gone missing.  Luke knew that the trip that she was on was to refind the Lost World and study living dinos.   Luke also has the diary with the directions on where the Lost World was.  So he, Nick, and Nick's father set out to find Luke's mother.  Along the way they find out that the German pilot was part of an international group set on world power and killing to get it.  So not only do they need to find Luke's mother, they must survive many attempts on their lives and find out who this group really is and what they want.