The Rockingdown Mystery
by Enid Blyton (William Collins, 1949)
A solid introduction to the ‘Barney’ (or ‘R’) mystery series. Standard Blyton characters Roger and Diana are superseded by their mischievous cousin Snubby, vagabond circus boy Barney and his monkey Miranda, and of course Snubby’s (actually Blyton’s daughters’) memorably madcap dog Loony.