Sleuth It Reader
Capture the flag by Kate Messner — This is the first in a series that introduces the Silver Jaguar Society, a secret group that protects historical and artistic items. It's a fast moving adventure that has a little bit of a funny bone. The second book in the series is called Hide and Seek
Jack Haldean is a WW I veteran, newspaper columnist, and writer of mystery novels. I like Jacqueline Winspear's Maisie Dobbs' series and Charles Todd's Ian Rutledge series and found Haldean's books a good read.