i'm reading this book called "fundamentals of piano practice" by Chuan Chang, although there are a number of people who are against his methods of practice and his technique, there are also people who have benefited from them, basically he suggests that we divide the piece into small sections and memorize them hands separate, then SLOWLY put them together... he gave a suggested a pracitce routine for Bach's invention #s 1, 4, and 8... i followed them and found them really helpful, but i have not done number 4 yet,,,
his book is downloadable in pdf form, just do a google search of it. good luck!