Encyclopedia Brown and the Case of the Secret UFOs - Donald J. Sobol Encyclopedia Brown and the Case of the Secret Pitch  - Donald J. Sobol Encyclopedia Brown Finds the Clues - Donald J. Sobol Encyclopedia Brown Gets His Man  - Leonard W. Shortall, Donald J. Sobol

Can't say enough good things about this series.  Written for kids but still a great read for adults on a nostalgia kick.