If you have a serious problem with your handwriting, or are just serious about improving your handwriting, try Teach Yourself Better Handwriting by Rosemary Sassoon. She is both a historian of handwriting and a physical therapist (for handwriting). Instead of presenting a model alphabet to copy, she has you analyze your natural writing style and figure out how to improve it. Her focus is to both improve the look of your writing and help you become more comfortable/fast.