Samuel Solomon's book Advanced Rhythm Studies is a great resource for learning and building up the skills to play complicated poly- and syncopated rhythms. The book drills the rhythmic "vocabulary," using marching as a rhythmic reference. The rhythmic studies are challenging but are approached in an accessible manner and built up gradually from basic patterns. Using this book will help all percussionists gain proficiency with complicated patterns and make them fun to play. A percussionist's must-have. For more info, click HERE.